PHY 201 - Module 10: Linear Momentum

In which of these processes is the momentum of the object conserved?

A skydiver (the object) with her parachute deployed falls toward the ground at a steady speed.

Two hockey players collide on the ice. Which statement reflects how we can apply conservation of momentum to this situation?

During the very brief collision the total momentum of the two players (the system) is a conserved quantity.

The standard units of momentum are kg*m/s. Which of these is an alternate way to express these units?

N*s

Can an object have more than one momentum at a given moment?

No, an object always has one unique velocity and one unique mass at any given moment.

During a complex collision between many objects, including object A and object C, the impulse exerted on object A by object C is equal to __________.

None of the listed responses is correct.

Playing in the rain, a little girl tackles a little boy. Just before she tackles him, the boy is running east at 3 m/s and the girl is running south at 4 m/s. After the tackle, the girl holds on and the two slide on the wet grass. Our system consists of just the two children. Before the tackle, in roughly what direction does the total momentum of the system point?

Somewhere south of east, but we cannot be any more specific than that.

Playing in the rain, a little girl tackles a little boy. Just before she tackles him, the boy is running east at 3 m/s and the girl is running south at 4 m/s. After the tackle, the girl holds on and the two slide on the wet grass. Our system consists of just the two children. Immediately after the tackle, what can we say about how the momenta of each child compare?

The momentum of both children will be in the same direction.

You observe two identical balls of putty headed directly toward each other at the same speed; what can you say about their total momentum?

They have zero total momentum.

Two cars experience a collision on a city road. Both drivers are using their brakes when the cars hit. Which statement is true?

Using the impulse approximation, conservation of momentum can be applied to the very brief time period of the collision itself (giving approximate results).

If some quantity, let's call it "Z," is conserved for a certain system, during a certain process, that means __________.

Z for that system does not change in any way during that process

If some quantity, let's call it "Z," is conserved for a certain system, during a certain process, that must mean __________.

any change in Z for parts of the system during the process is offset by an equal but opposite change for the Z of other parts of the system

The impulse approximation is used in situations where __________.

external forces on the system are present, but they are small compared to the large, brief internal forces between parts of the system

Momentum __________.

is a vector, with a magnitude and a direction

The units for momentum are __________.

kg*m/s

If two cars have the same mass and speed they __________.

might have the same momentum but might not

Two asteroids are flying through space, each with an unknown momentum, and The equation shows vector p sub 1.The equation shows vector p sub 2.The equation shows vector p sub x.. Which of these is a true statement about the x-component of their total momentum, ?

must have a magnitude between zero and the sum of the magnitudes of their individual momenta. Meaning The equation shows zero is less than or equal to the magnitude of vector p sub x which is less than the quantity of the magnitude of vector p sub 1 plus the magnitude of the vector p sub 2..

The momentum of a system is conserved during a certain process only if __________.

no net external force is exerted on the system during that process

The change in an object's momentum during a certain time interval is equal to __________.

the net force exerted on the object times the duration of the time interval

During a large, multi-object collision that involves object C, the change in the momentum of object C is equal to __________.

the net impulse exerted on object C

The momentum of an object is defined as __________.

the object's mass times its velocity

The image shows two balls (1 and 2) that are going to collide as they approach the point marked . Ball 1 has a mass of 2m and speed v, while ball 2 has mass m and speed 2v. Both balls are moving at 45º angles with respect to the vertical. Our system consists of just the two balls and is isolated from external forces. Just before the collision __________.

the total horizontal component of the momentum of the system is zero

The image shows two balls (1 and 2) that are going to collide as they approach the point marked . Ball 1 has a mass of 2m and speed v, while ball 2 has mass m and speed 2v. Both balls are moving at 45º angles with respect to the vertical. Our system consists of just the two balls and is isolated from external forces. Just after the collision __________.

the total horizontal component of the momentum of the system must be zero

The image shows two balls about have a head-on collision. Ball A has a mass m and speed of 2v, whereas ball B has mass 2m and speed v. Our system consists of just the two balls and is isolated from external forces. Just before the collision __________.

the total momentum of the system is zero

The image shows two balls about have a head-on collision. Ball A has a mass m and speed of 2v, whereas ball B has mass 2m and speed v. Our system consists of just the two balls and is isolated from external forces. Just before the collision __________.

the total momentum of the system must be zero