A Slowly Moving Ship Can Have a Greater Momentum Than a Fast-moving Racing Car When
Momentum and Collisions Review
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Part B: Multiple Pick
vi. Which of the post-obit objects have momentum? Include all that apply.
a. An electron is orbiting the nucleus of an atom.
b. A UPS truck is stopped in front of the school building.
c. A Yugo (a compact car) is moving with a constant speed.
d. A small flea walking with constant speed across Fido's back.
east. The high school building rests in the middle of town.
Reply: A, C, and D
Momentum can be idea of equally mass in motion. An object has momentum if it has its mass in motion. Information technology matters not whether the object is of big mass or modest mass, moving with constant speed or accelerating; if the object is MOVING, and so it has momentum!
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7. A truck driving along a highway road has a large quantity of momentum. If it moves at the same speed but has twice every bit much mass, its momentum is ________________.
| a. zero | b. quadrupled | c. doubled | d. unchanged |
Respond: C
Momentum is directly related to the mass of the object. So for the same speed, a doubling of mass leads to a doubling of momentum.
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8. Truthful or FALSE:
A ball is dropped from the same height upon various apartment surfaces. For the same collision time, impulses are smaller when the well-nigh bouncing take place.
Answer: B
Since being dropped from the same height, the balls volition be moving with the same pre-collision velocity (bold negligible air resistance). Upon standoff with the ground, the velocity will take to be reduced to nil - that is, the brawl will cease moving downwards. This decrease in velocity constitutes the first portion of the velocity change. If the ball bounces, so there is an additional velocity modify sending the ball back upward contrary the original management. Thus, for the same standoff time, bouncing involves a greater velocity modify, a greater momentum modify, and therefore a greater impulse.
nine. Consider a karate expert. During a talent testify, she executes a swift blow to a cement block and breaks it with her bare hand. During the collision between her manus and the block, the ___.
- time of impact on both the block and the expert's manus is the same
- force on both the block and the skillful's hand have the aforementioned magnitude
- impulse on both the block and the expert'due south mitt have the aforementioned magnitude
- all of the in a higher place.
- none of the to a higher place.
Respond: D
In any collision, at that place are always four quantities which are the same for both objects involved in the collision. Each object experiences the aforementioned strength (Newton'south third police force) for the same amount of fourth dimension, leading to the same impulse, and subsequently the same momentum alter. Just the acceleration and the velocity change can differ for the two colliding objects. The lower mass object e'er receives the greater velocity change and acceleration.
ten. Information technology is Not possible for a rocket to advance in outer space because ____. Listing all that employ.
- there is no air in space
- there is no friction in space
- there is no gravity in outer space
- ... nonsense! Rockets practise accelerate in outer space.
Answer: D
Rockets accelerate in outer space by means of Newton's 3rd law of motion. It does not matter that in that location is no air outside of the rocket. Rockets produce their ain gas by burning fuels. The combustion of rocket fuels produces gaseous products. The rocket's thrusters push these gases backwards (or rightwards, or leftwards, or ...) and the gases push the rocket forrard (or leftwards, or rightwards, or ...). Thus, rockets indeed can and practise advance in outer infinite.
11.In club to catch a ball, a baseball player naturally moves his or her hand backward in the direction of the ball's motion once the ball contacts the hand. This habit causes the forcefulness of bear upon on the players paw to be reduced in size principally because ___.
- the resulting impact velocity is lessened
- the momentum change is decreased
- the fourth dimension of touch is increased
- the time of impact is decreased
- none of these
Answer: C
Increasing the time over which the ball's momentum is brought to 0 will decrease the force required to end it. Suppose a ball is coming at y'all with 100-units of momentum. An impulse of 100-units would exist required to stop the ball. Regardless of how the impulse is accomplished (big F, little t or niggling F, big t), there must be 100-units of it. Imparting such an impulse over a long time results in a modest force.
12. Suppose that Paul D. Trigger fires a bullet from a gun. The speed of the bullet leaving the muzzle volition be the same as the speed of the recoiling gun ____.
- considering momentum is conserved
- because velocity is conserved
- considering both velocity and momentum are conserved
- only if the mass of the bullet equals the mass of the gun
- none of these
Answer: D
In whatsoever collision or explosion involving two objects, the momentum alter for each object is the same. So both the bullet and the gun encounter the same momentum change. The momentum alter is but the mass multiplied by the velocity change. Thus, the velocity change would merely be the aforementioned if their masses were the same. Otherwise, the smaller-mass object receives a greater velocity modify.
xiii. Suppose that you're driving downwardly the highway and a moth crashes into the windshield of your car. Which undergoes the greater change is momentum?
| a. the moth | b. your car | c. both the same |
Reply: C
In any collision, there are always four quantities which are the aforementioned for both objects involved in the collision. Each object experiences the same force (Newton's third law) for the same corporeality of time, leading to the same impulse, and afterward the same momentum change. Only the acceleration and the velocity change can differ for the two objects. The object with the least mass always receives the greatest velocity change and dispatch.
14. Suppose that you lot're driving downwardly the highway and a moth crashes into the windshield of your car. Which undergoes the greater force?
| a. the moth | b. your car | c. both the same |
Reply: C
In any collision, there are always four quantities which are the same for both objects involved in the collision. Each object experiences the same forcefulness (Newton's third law) for the same amount of time, leading to the same impulse, and subsequently the aforementioned momentum change. Merely the dispatch and the velocity change can differ for the ii objects. The object with the least mass ever receives the greatest velocity modify and dispatch.
15. Suppose that you're driving downwards the highway and a moth crashes into the windshield of your car. Which undergoes the greater impulse?
| a. the moth | b. your car | c. both the same |
Answer: C
In any standoff, there are always four quantities which are the same for both objects involved in the standoff. Each object experiences the aforementioned force (Newton'southward third law) for the same amount of time, leading to the same impulse, and subsequently the same momentum modify. Only the dispatch and the velocity change can differ for the 2 objects. The object with the to the lowest degree mass ever receives the greatest velocity change and dispatch.
sixteen. Suppose that you're driving down the highway and a moth crashes into the windshield of your car. Which undergoes the greater acceleration?
| a. the moth | b. your automobile | c. both the aforementioned |
Respond: A
In whatsoever collision, in that location are always four quantities which are the same for both objects involved in the standoff. Each object experiences the same force (Newton'south third law) for the same amount of fourth dimension, leading to the same impulse, and subsequently the same momentum change. Just the dispatch and the velocity modify tin differ for the two objects. The object with the least mass always receives the greatest velocity change and acceleration.
| 17. Three boxes, X, Y, and Z, are at rest on a table every bit shown in the diagram at the right. The weight of each box is indicated in the diagram. The cyberspace or unbalanced force acting on box Y is _____. |  | |||||
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Answer: Due east
If an object is at rest, then all the forces acting upon the object must be nothing. The internet force on any one of the boxes is 0 Newtons. Subsequently, in each case, the support force (which we take chosen the "normal forcefulness throughout this course) acting upwards on any of the boxes must be equal to the force of gravity on that box (i.e., the weight) plus the amount of load exerted from above (which would be equivalent to the weight of the other boxes located above the box). Then for box Y, the support strength acting upward would be equal to nine Due north while the net strength is however 0 Newtons. And for box Z, the back up force is xix N, sufficient to residuum the ten-N gravitational forcefulness plus the 9-Northward of force resulting from the other ii boxes begetting down on it.
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18. In a physics experiment, ii equal-mass carts roll towards each other on a level, low-friction rail. I cart rolls rightward at two chiliad/southward and the other cart rolls leftward at ane m/s. Afterward the carts collide, they couple (adhere together) and ringlet together with a speed of _____________. Ignore resistive forces.
| a. 0.5 m/s | b. 0.33 m/s | c. 0.67 1000/s | d. 1.0 yard/south | e. none of these |
Answer: A
Use 1 kg as the mass of the carts (or whatsoever number you wish) and and so set the expression for initial total momentum equal to the expression for the final total momentum:
Now solve for v using the proper algebraic steps.
1 kg•k/s = (two kg)v
(1 kg•thou/due south) / (2 kg) = five
0.5 m/s = five
19. A physics cart rolls along a low-friction runway with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is ____.
| a. naught | b. four times equally large | c. twice as large | d. unchanged |
Answer: C
The momentum of an object is calculated equally the product of mass and velocity. Thus, the momentum is directly proportional to the mass of the object. If the mass of an object is somehow doubled, the momentum is doubled as well.
twenty. The firing of a bullet by a burglarize causes the rifle to recoil backwards. The speed of the rifle's recoil is smaller than the bullet's frontwards speed because the ___.
| a. strength confronting the rifle is relatively small | b. speed is mainly concentrated in the bullet |
| c. rifle has lots of mass | d. momentum of the rifle is unchanged |
| eastward. none of these |
Answer: C
Please don't respond A (for it will make Newton curlicue over in his grave and he's getting quite tired of that). Perhaps yous've heard that "for every action, there is an equal and opposite ...". Option B is invalid; speed is not something that becomes concentrated or squeezed into an object. Choice D is invalid; ask anyone who's fired a burglarize if the rifle is set into motility by the firing of the bullet. (Of form, since it is prepare in motion, its momentum is not unchanged.) Because of the large mass of the burglarize, the acceleration and the recoil speed of the rifle is small.
21. Two objects, A and B, have the aforementioned size and shape. Object A is twice equally massive as B. The objects are simultaneously dropped from a high window on a alpine edifice. (Fail the effect air resistance.) The objects will reach the ground at the same fourth dimension simply object A volition have a greater ___. Choose all that utilize.
| a. speed | b. acceleration | c. momentum |
| d. none of the above quantities will be greater | ||
Respond: C
The two objects free-fall at the same rate of acceleration, thus giving them the same speed when they hitting the ground. The heavier object however has more momentum since momentum takes into account both the speed and the mass of the object (p=m*five).
22. Cars are equipped with padded dashboards. In collisions, the padded dashboards would exist safer than non-padded ones because they ____. List all that apply.
| a. increase the impact time | b. decrease an occupant's impulse |
| c. decrease the bear on forcefulness | d. none of the in a higher place |
Answer: Air conditioning
Both A and C are correct. Padded dashboard serve to increase the time over which the momentum of a passenger is reduced to zero. With this increase in time, there is a decrease in forcefulness (big T, niggling f).
The impulse interim upon the rider is not changed. The passenger still must have his/her mass slowed downwards from the pre-impact velocity to zero velocity. This means the velocity change is the aforementioned whether the collision occurs with a padded dashboard, an air handbag or a glass windshield. Since the velocity change is independent of the collision time, the momentum change and the required impulse are also independent of the collision time.
23. A 4 kg object has a momentum of 12 kg•m/s. The object's speed is ___ thousand/southward.
| a. 3 | b. iv | c. 12 | d. 48 | e. none of these. |
Answer: A
This is a relatively uncomplicated plug-and-chug into the equation p=thousand*five with m=four kg and p=12 kg•m/s.
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24. A wad of chewed chimera mucilage is moving with ane unit of momentum when it collides with a heavy box that is initially at rest. The gum sticks to the box and both are set up in motion with a combined momentum that is ___.
| a. less than 1 unit of measurement | b. i unit | c. more 1 unit of measurement | d. non enough information |
| Answer: B Before the collision, the total system momentum is 1 unit - all due to the motion of the wad of glue. Since momentum must be conserved, the total momentum of the box and gum after the collision must also be 1 unit of measurement. |
25. A relatively large force acting for a relatively long corporeality of time on a relatively small mass volition produce a relatively ______. Listing all that apply.
| a. small velocity change | b. large velocity modify |
| c. small momentum change | d. small-scale acceleration |
Reply: B
A large force acting upon a small mass will result in a large acceleration (a=F/1000) and afterwards a large velocity change (Delta v = a*t). This rules out choices A and D. A large force and for a long time will outcome in a large impulse and therefore a large momentum change. This rules out choice C.
26. Consider the concepts of piece of work and free energy (presuming yous have already studied it) and those of impuse and momentum. Force and fourth dimension is related to momentum change in the same style as force and displacement pertains to ___________.
| a. impulse | b. piece of work | c. energy alter | d. velocity | due east. none of these. |
Respond: C
A forcefulness multiplied by a fourth dimension gives an impulse which will cause (and be equal to) a momentum alter. In the same manner, a force multiplied past a displacement gives work which volition crusade (and be equal to) an energy modify. Accept the time to reread those two sentences because it relates two big concepts.
27. A 5-Northward force is applied to a 3-kg ball to change its velocity from +9 thou/due south to +3 thousand/southward. This impulse causes the momentum modify of the brawl to exist ____ kg•g/due south.
| a. -2.five | b. -10 | c. -18 | d. -45 | e. none of these |
Answer: C
Don't make this harder than information technology is; the momentum change of an object tin be constitute if the mass and the velocity alter are known. In this equation, 1000=3 kg and the velocity change is -six thousand/due south. When finding the velocity modify, always subtract the initial velocity from the final velocity (vf - vi).
In that location is a second means of determining the momentum change of an object (though information technology does non need to be used in this trouble). The momentum alter can also exist found if the force and the time are known. Multiplying strength*time yields the impulse and the impulse equals the momentum change.
28. A 5-N force is applied to a 3-kg brawl to modify its velocity from +9 thousand/south to +iii 1000/s. The impulse experienced by the ball is ____ N•s.
| a. -ii.5 | b. -ten | c. -18 | d. -45 | due east. none of these |
Answer: C
Impulse is defined as a force acting upon and object for a given amount of fourth dimension. Impulse can be computed by multiplying force*fourth dimension. Just in this trouble, the time is not known. Never fear - the impulse equals the momentum modify. The momentum change in this problem is -18 kg•m/s (see question #27 ). Thus, the impulse is -18 N•s.
29. A five-N force is practical to a 3-kg ball to change its velocity from +9 yard/s to +iii m/s. The impulse is encountered by the ball for a time of ____ seconds.
| a. 1.8 | b. 2.v | c. 3.6 | d. 10 | e. none of these |
Respond: C
Use the impulse momentum change theorem with F=five N, m=3 kg and Delta five=-half-dozen m/s. Solving for fourth dimension involves the post-obit steps.
t = 3.6 s
30. When a mass Yard experiences a velocity modify of v in a fourth dimension of t , it experiences a force of F . Assuming the same velocity alter of 5 , the strength experienced by a mass of 2M in a fourth dimension of (1/2)t is ____.
| a. 2F | b. 4F | c. (ane/2)*F | d. (1/4)*F | e. none of these |
Answer: B
The impulse-momentum change theorem states that F*t = m*(Delta vel.). This equation tin can be rearranged to locate the F by itself on one side of the equation; rearranging yields
The equation shows that force is directly related to the mass, directly related to the modify in velocity, and inversely related to the time. And then any change in mass volition upshot in the same modify in force; and any change in time will result in the inverse effect upon the forcefulness. In this case, doubling the mass (from M to 2M) will double the force and halving the time (from t to 1/ii-t) will double the force. The combined consequence of these two changes will brand the new force four times bigger than the old force. This is a case of where equations tin be a guide to thinking about how a alter in ane variable (or ii variables) impacts other dependent variables.
31. When a mass M experiences a velocity alter of v in a time of t , it experiences a force of F . Assuming the same velocity change of five , the strength experienced by a mass of 2M in a time of (ane/4)t is ____.
| a. 2F | b. 8F | c. (one/ii)*F | d. (one/8)*F | e. none of these |
Answer: B
The impulse-momentum change theorem states that F*t = m*(Delta vel.). This equation tin be rearranged to locate the F by itself on one side of the equation; rearranging yields
The equation shows that force is directly related to the mass, directly related to the change in velocity, and inversely related to the time. So any change in mass will result in the same change in force; and any change in time volition result in the changed effect upon the force. In this case, doubling the mass (from Grand to 2M) volition double the strength and quartering the time (from t to 1/4-t) will quadruple the force. The combined effect of these two changes will make the new force eight times bigger than the old strength. This is a case of where equations tin exist a guide to thinking about how a change in 1 variable (or two variables) impacts other dependent variables.
32. When a mass Chiliad experiences a velocity alter of v in a time of t , it experiences a forcefulness of F . Assuming the same velocity change of v , the force experienced by a mass of (ane/2)M in a time of (1/2)t is ____.
| a. 2F | b. 4F | c. (i/2)*F | d. (ane/four)*F | due east. none of these |
Answer: E
The impulse-momentum change theorem states that F*t = 1000*(Delta vel.). This equation can exist rearranged to locate the F by itself on one side of the equation; rearranging yields
The equation shows that strength is directly related to the mass, directly related to the change in velocity, and inversely related to the time. So whatsoever alter in mass will issue in the same change in force; and any change in time will result in the inverse upshot upon the force. In this example, halving the mass (from M to 1/ii-Grand) will half the force and halving the time (from t to ane/2-t) volition double the strength. The combined result of these two changes will make the new forcefulness the same size every bit the old forcefulness. This is a case of where equations can be a guide to thinking about how a change in one variable (or ii variables) impacts other dependent variables.
33. When a mass M experiences a velocity change of v in a time of t , it experiences a force of F . Assuming the same velocity modify of v , the force experienced by a mass of (i/2)M in a time of 4t is ____.
| a. 2F | b. 8F | c. (1/2)*F | d. (1/8)*F | e. none of these |
Respond: D
The impulse-momentum change theorem states that F*t = thousand*(Delta vel.). This equation tin can be rearranged to locate the F by itself on one side of the equation; rearranging yields
The equation shows that force is straight related to the mass, direct related to the change in velocity, and inversely related to the time. So any change in mass volition result in the same alter in force; and any change in time will result in the changed effect upon the forcefulness. In this case, halving the mass (from M to ane/ii-1000) volition halve the force and quadrupling the time (from t to 4t) will quarter the strength. The combined effect of these 2 changes will make the new force eight times smaller (i.eastward., one-eighth the size) than the old force. This is a instance of where equations tin be a guide to thinking almost how a change in 1 variable (or two variables) impacts other dependent variables.
34. A 0.5-kg ball moving at 5 m/s strikes a wall and rebounds in the contrary direction with a speed of 2 m/s. If the impulse occurs for a time duration of 0.01 south, then the average force (magnitude only) acting upon the ball is ____ Newtons.
| a. 0.fourteen | b. 150 | c. 350 | d. 500 | e. none of these |
Answer: C
This is a relatively uncomplicated plug-and-chug into the equation
with yard=0.5 kg, t=0.01 due south and Delta vel.=-7 m/southward. (The change in velocity is -seven m/s since the ball must start irksome down from 5 m/southward to 0 m/southward and so exist thrown back in the opposite direction at 2 m/s.) Using these numbers and solving for strength yields -350 N. The magnitude of the strength is 350 N and the "-" sign indicates the direction of the forcefulness.
35. If mass and collision time are equal, then impulses are greater on objects which rebound (or bounce).
Answer: A
The impulse is equal to the momentum change. And when there is a rebound, the momentum alter is larger since there is a larger velocity alter. For instance, a ball thrown at a wall at 5 m/south may rebound at -3 m/due south yielding a velocity change of -8 thousand/south. An egg thrown at the aforementioned wall at the aforementioned speed of v yard/due south hits and stops, thus yielding a velocity alter of -5 m/s. More velocity change ways more momentum change and thus more impulse.
36. Consider the head-on collision between a lady problems and the windshield of a loftier speed bus. Which of the following statements are true? List all that apply.
- The magnitude of the force encountered by the bug is greater than that of the bus.
- The magnitude of the impulse encountered past the bug is greater than that of the bus.
- The magnitude of the momentum change encountered by the bug is greater than that of the motorcoach.
- The magnitude of the velocity change encountered by the issues is greater than that of the passenger vehicle.
- The magnitude of the acceleration encountered by the problems is greater than that of the bus.
Respond: D and E
In any collision betwixt two objects, the force, impulse, and momentum change are the same for each object. (This makes statements A, B, and C simulated.) Nevertheless, the smaller mass object encounters a greater acceleration and velocity change. (This makes statements D and E true).
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