Momentum and Collisions

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 car c. both the same

A

In a physics experiment, two equal-mass carts roll towards each other on a level, low-friction track. One cart rolls rightward at 2 m/s and the other cart rolls leftward at 1 m/s. After the carts collide, they couple (attach together) and roll together with a speed of _____________. Ignore resistive forces. a. 0.5 m/s b. 0.33 m/s c. 0.67 m/s d. 1.0 m/s e. none of these

A (2 kg•m/s) - (1 kg•m/s) = (2 kg) v 1 kg•m/s = (2 kg)v (1 kg•m/s) / (2 kg) = v 0.5 m/s = v

Which of the following 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. e. The high school building rests in the middle of town.

A, C and D

A 4 kg object has a momentum of 12 kg•m/s. The object's speed is ___ m/s. a. 3 b. 4 c. 12 d. 48 e. none of these.

A: p=m*v with m=4 kg and p=12 kg•m/s.

Which of the following statements are true about collisions? a) Two colliding objects will exert equal forces upon each other even if their mass is significantly different. b) During a collision, an object always encounters an impulse and a change in momentum. c) During a collision, the impulse which an object experiences is equal to its velocity change. d) The velocity change of two respective objects involved in a collision will always be equal. e) While individual objects may change their velocity during a collision, the overall or total velocity of the colliding objects is conserved. f) In a collision, the two colliding objects could have different acceleration values. g) In a collision between two objects of identical mass, the acceleration values could be different. h)Total momentum is always conserved between any two objects involved in a collision. i)When a moving object collides with a stationary object of identical mass, the stationary object encounters the greater collision force. j)When a moving object collides with a stationary object of identical mass, the stationary object encounters the greater momentum change. k)A moving object collides with a stationary object; the stationary object has significantly less mass. The stationary object encounters the greater collision force. l)A moving object collides with a stationary object; the stationary object has significantly less mass. The stationary object encounters the greater momentum change.

ABF

Cars are equipped with padded dashboards. In collisions, the padded dashboards would be 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 impact force d. none of the above

AC

Which of the following statements are true about momentum? a) Momentum is a vector quantity. b) The standard unit on momentum is the Joule. c) An object with mass will have momentum. d) An object which is moving at a constant speed has momentum. e) An object can be traveling eastward and slowing down; its momentum is westward. f)Momentum is a conserved quantity; the momentum of an object is never changed. g) The momentum of an object varies directly with the speed of the object. h) Two objects of different mass are moving at the same speed; the more massive object will have the greatest momentum. i) A less massive object can never have more momentum than a more massive object. j) Two identical objects are moving in opposite directions at the same speed. The forward moving object will have the greatest momentum. k) An object with a changing speed will have a changing momentum.

ADGHK

Which of the following statements are true about elastic and inelastic collisions? Perfectly elastic and perfectly inelastic collisions are the two opposite extremes along a continuum; where a particular collision lies along the continuum is dependent upon the amount kinetic energy which is conserved by the two objects. Most collisions tend to be partially to completely elastic. Momentum is conserved in an elastic collision but not in an inelastic collision. The kinetic energy of an object remains constant during an elastic collision. Elastic collisions occur when the collision force is a non-contact force. Most collisions are not inelastic because the collision forces cause energy of motion to be transformed into sound, light and thermal energy (to name a few). A ball is dropped from rest and collides with the ground. The higher that the ball rises upon collision with the ground, the more elastic that the collision is. A moving air track glider collides with a second stationary glider of identical mass. The first glider loses all of its kinetic energy during the collision as the second glider is set in motion with the same original speed as the first glider. Since the first glider lost all of its kinetic energy, this is a perfectly inelastic collision. The collision between a tennis ball and a tennis racket tends to be more elastic in nature than a collision between a halfback and linebacker in football.

AEFGI

A wad of chewed bubble gum is moving with 1 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 in motion with a combined momentum that is ___. a. less than 1 unit b. 1 unit c. more than 1 unit d. not enough information

B

A relatively large force acting for a relatively long amount of time on a relatively small mass will produce a relatively ______. List all that apply. a. small velocity change b. large velocity change c. small momentum change d. small acceleration

B: A large force acting upon a small mass will result in a large acceleration (a=F/m) and subsequently a large velocity change (Delta v = a*t). This rules out choices A and D. A large force and for a long time will result in a large impulse and therefore a large momentum change. This rules out choice C.

Which of the following statements are true about impulse? a) Impulse is a force. b) Impulse is a vector quantity. c) An object which is traveling east would experience a westward directed impulse in a collision. d) Objects involved in collisions encounter impulses. e) The Newton is the unit for impulse. f) The kg•m/s is equivalent to the units on impulse. g) An object which experiences a net impulse will definitely experience a momentum change. h) In a collision, the net impulse experienced by an object is equal to its momentum change. i) A force of 100 N acting for 0.1 seconds would provide an equivalent impulse as a force of 5 N acting for 2.0 seconds.

BDFGHI

Which of the following are true about the relationship between momentum end energy? a) Momentum is a form of energy. b) If an object has momentum, then it must also have mechanical energy. c) If an object does not have momentum, then it definitely does not have mechanical energy either. d) Object A has more momentum than object B. Therefore, object A will also have more kinetic energy. e) Two objects of varying mass have the same momentum. f) The least massive of the two objects will have the greatest kinetic energy.

BE

A physics cart rolls along a low-friction track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is ____. a. zero b. four times as large c. twice as large d. unchanged

C

A truck driving along a highway road has a large quantity of momentum. If it moves at the same speed but has twice as much mass, its momentum is ________________. a. zero b. quadrupled c. doubled d. unchanged

C

Consider the concepts of work and energy (presuming you have already studied it) and those of impuse and momentum. Force and time is related to momentum change in the same manner as force and displacement pertains to ___________. a. impulse b. work c. energy change d. velocity e. none of these.

C

In order 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 force of impact on the players hand to be reduced in size principally because ___. A)the resulting impact velocity is lessened B)the momentum change is decreased C)the time of impact is increased D)the time of impact is decreased E) none of these

C

Suppose that you're driving down 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

C

Suppose that you're driving down 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

C

Suppose that you're driving down 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

C

The firing of a bullet by a rifle causes the rifle to recoil backwards. The speed of the rifle's recoil is smaller than the bullet's forward speed because the ___. a. force against 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 e. none of these

C

Two objects, A and B, have the same size and shape. Object A is twice as massive as B. The objects are simultaneously dropped from a high window on a tall building. (Neglect the effect air resistance.) The objects will reach the ground at the same time but object A will have a greater ___. Choose all that apply. a. speed b. acceleration c. momentum d. none of the above quantities will be greater

C

If a force is exerted on an object, which statement is true? a) a large force always produces a large change in the object's momentum b) a large force produces a large change in the object's momentum only if the force is applied over a very short time interval c) A small force applied over a long time interval can produce a large change in the object's momentum d) a small force always produces a large change in the object's momentum

C A small force applied over a long time interval can produce a large change in the object's momentum

When comparing the momentum of two moving objects, which of the following is correct? a) The object with the higher velocity will have less momentum if the masses are equal. b) The more massive object will have less momentum if its velocity is greater. c) The less massive object will have less momentum if the velocities are the same. d) The more massive object will have less momentum if the velocities are the same.

C The less massive object will have less momentum if the velocities are the same.

A 5-N force is applied to a 3-kg ball to change its velocity from +9 m/s to +3 m/s. The impulse experienced by the ball is ____ N•s. a. -2.5 b. -10 c. -18 d. -45 e. none of these

C: Impulse is defined as a force acting upon and object for a given amount of time. Impulse can be computed by multiplying force*time. But in this problem, the time is not known. Never fear - the impulse equals the momentum change. The momentum change in this problem is -18 kg•m/s Thus, the impulse is -18 N•s.

A 5-N force is applied to a 3-kg ball to change its velocity from +9 m/s to +3 m/s. This impulse causes the momentum change of the ball to be ____ kg•m/s. a. -2.5 b. -10 c. -18 d. -45 e. none of these

C: the momentum change of an object can be found if the mass and the velocity change are known. In this equation, m=3 kg and the velocity change is -6 m/s. When finding the velocity change, always subtract the initial velocity from the final velocity (vf - vi).

It is NOT possible for a rocket to accelerate in outer space because ____. List all that apply. A)there is no air in space B)there is no friction in space C)there is no gravity in outer space D)... nonsense! Rockets do accelerate in outer space.

D

Suppose that Paul D. Trigger fires a bullet from a gun. The speed of the bullet leaving the muzzle will be the same as the speed of the recoiling gun ____. A) because momentum is conserved B) because velocity is conserved C) because both velocity and momentum are conserved D)only if the mass of the bullet equals the mass of the gun E)none of these

D

Consider a karate expert. During a talent show, she executes a swift blow to a cement block and breaks it with her bare hand. During the collision between her hand and the block, the ___. a)time of impact on both the block and the expert's hand is the same b)force on both the block and the expert's hand have the same magnitude c) impulse on both the block and the expert's hand have the same magnitude d) all of the above. e) none of the above.

D - All of the above

Three boxes, X, Y, and Z, are at rest on a table as shown in the diagram at the right. The weight of each box is indicated in the diagram. The net or unbalanced force acting on box Y is _____. a. 4 N down b. 5 N down c. 5 N up d. 10 N up e. zero

E

TRUE or FALSE: A ball is dropped from the same height upon various flat surfaces. For the same collision time, impulses are smaller when the most bouncing take place.

False

A roller coaster climbs up a hill at 4m/s and then zips down the hill at 30m/s. The momentum of the roller coaster

is greater up the hill than down the hill

What equation can be used to directly calculate an object's momentum, p?

p=mv

A rubber ball moving at the speed of 5m/s hits a flat wall and returned to the thrower at 5m/s. The magnitude of the momentum of the rubber ball

remained the same