physics: momentum, impulse, & collisions test

Define momentum.

a vector quantity defined as the product of the mass times the velocity

Momentum is a ______ (vector/scalar) quantity.

vector

T/F: Momentum is directly proportional to the mass and speed of an object

True

The SI base unit of momentum is _______.

kg * m/s

What is the formula for momentum?

P = mv

Why is the variable for momentum “p”?

“Progress” in movement

Define impulse.

Impulse is the product of the force and the change in time over which the force acts on an object; it described as the change in momentum over time.

Impulse is described as the change in ________.

momentum

In what real-world ways is the impulse-momentum theorem used?

• vehicle safety

• airbags

• stopping distance

_______ (larger/smaller) objects in motion have a greater momentum; _______ (larger/smaller) objects in motion have a lower momentum.

larger; smaller

both mass and velocity are _______ (directly/inversely) proportional to momentum.

directly

Impulse relates the ______ of impact and _____ interval with the change in _________.

force; time; momentum

if the time interval is ________ (increased/decreased), then the force of impact is ________ (increased/decreased).

increased; decreased

The force of impact and time interval are ________ (directly/inversely) proportional to impulse.

directly (?)

The ______-______ theorem relates to Newton’s 2nd Law.

impulse-momentum

The momentum of an object is in the same direction as its

a) acceleration

b) force

c) velocity

d) inertia

c) velocity

Which of the following has the greatest momentum?

a) a ball sitting on the porch

b) a car accelerating from a stop sign

c) a skateboard rolling down an incline

d) a student walking to their class

b) a car accelerating from a stop sign

When a space shuttle takes off, it increases its velocity. How does this change in velocity affect the momentum?

a) the momentum increases

b) the momentum decreases

c) the momentum remains constant

d) the momentum changes direction

a) the momentum increases

As a rocket takes off, it burns fuel and its mass decreases. How does the change in mass affect its momentum?

a) the momentum increases

b) the momentum decreases

c) the momentum remains constant

d) the momentum changes direction

b) the momentum decreases

Student A and Student B are debating between whether or not a small car and a large SUV of a greater mass can have the same momentum. Student A is positive that they can not have the same momentum, but the Student B argues otherwise. Which of the following is an example Student B can give to Student A to prove their point? (Select all that apply.)

I. The car and SUV can have the same momentum if they have the same velocity.

II. The car and SUV can have the same momentum if their velocities are both zero.

III. The car and SUV can have the same momentum if the car is moving with a greater velocity than the SUV.

IV. The car and SUV can have the same momentum if the product of the car’s mass and velocity is equal to the product of the SUV’s mass and velocity.

a) I and II

b) II and III

c) II and IV

d) III and IV

d) III and IV

State the law of conservation of momentum.

The total momentum of all objects interacting with one another remains constant, regardless of the nature of the forces between the objects

Conservation of momentum is true for objects in an _______ (open/closed) system.

closed

What defines a closed system?

It is isolated— not influenced by outside forces.

What is the equation for conservation of momentum? Label each variable and include the SI base units.

(m₁v₁ + m₂v₂)_i = (m₁v₁ + m₂v₂)_f

• m= mass (kg)

• v= velocity (m/s)

How are explosions described in terms of conservation of momentum?

collisions and objects pushing away from each other

Conservation of momentum illustrates Newton’s ____ law.

3rd

Falling on a soft surface hurts less than falling on a hard surface because the time is increased and the _____ is decreased.

force

The equation for impulse is qual to

J = Ft

During collisions in a closed system, momentum is ______.

conserved

Momentum is a vector quantity because of _____.

velocity

For collisions between equal-mass objects, each object has the _____ acceleration.

same

How are collisions defined in physics?

when energy is transferred from one object to another

Kinetic energy is the energy of _______ and momentum is the _____ of that motion.

motion; quantity

What are the 2 basic types of collisions in physics?

Elastic and inelastic

An _____ ______ occurs when two objects collide and do not bounce away form each other.

inelastic collision

During an inelastic collision, momentum is __________ (conserved/not conserved) and kinetic energy is __________ (conserved/not conserved)

conserved; not conserved

During a perfectly inelastic collision, objects _____ _______ and their final velocities are the _____.

stick together; same

An _____ ______ occurs when two objects bounce apart when they collide.

elastic collision

During an elastic collision, momentum and kinetic energy are _______ (conserved/not conserved).

conserved

Summer and Tom are both holding exercise balls while running at each other. This is an example of an ________ collision.

elastic

During any collision, total _______ remains constant.

momentum

When a collision occurs, energy is lost as: (3 things)

• heat

• sound

• deformation

Elastic collisions occur when two objects collide and ______ off one another and move separately.

bounce

Both total _____ and ____ _____ are conserved during an elastic collision.

momentum; kinetic energy

Inelastic collisions occur when two objects collide, ______, and move off ________.

deform; separately

Total momentum is ______ during a perfectly inelastic collision. Kinetic energy _______ (increases/decreases)

conserved; decreases

A paintball hitting a barrier is an example of an ________ collision.

inelastic

Explosions occur when two objects start ______ and then …

together; push apart or detach from each other

Total momentum is ________ during an explosion. Kinetic energy ______ (increases/decreases)

decreases

In a collision between two objects, both objects experience forces that are equal in ______ and opposite in direction.

magnitude

A(n) ______ ______ is a system that is free from the influence of a net external force that alters the momentum of the system; for example, large frictional values are a net external force.

isolated system

Newton’s ___ law can be used to describe collisions.

3rd

More correctly in physics, forces cause acceleration, not _______.

motion

_______ of objects during a collision are not necessarily equal in magnitude because they are dependent on force and mass.

accelerations

During an explosion, an internal ______ acts in order to propel the parts of a system into a va riety of directions.

impulse

An impulse causes and is equal to a ______ in momentum.

change

The vector sum of all _______ parts of a system can be added to determine the total momentum after an explosion.

individual

Forces during a collision are equal in magnitude but opposite in direction, and the _____ massive object recieves the greatest acceleration.

least

A collision results in a _____ being applied to two colliding objects.

force

A large object collides with a small stationary object. The momentum…

a) of the large object decreases, and the momentum of the smaller object  increases. 

b) of the large object increases, and the momentum of the smaller object  decreases. 

c) of the large object equals zero, and the momentum of the smaller object equals  zero. 

d) does not change for either object.

a) of the large object decreases, and the momentum of the smaller object increases.

Two figure skaters are facing each other. One skater has a mass of 60 kg and  the other has a mass of 70 kg. If the skaters push away from each other …

a) the 60 kg skater’s momentum will decrease. 

b) their momenta is equal but opposite. 

c) their total momenta will double.  

d) their total momenta will increase. 

b) their momenta is equal but opposite. 

Two objects move separately after colliding, and both the total momentum and  total kinetic energy are conserved. What type of collision occurred? 

a) Elastic 

b) Perfectly inelastic 

c) Inelastic  

d) Explosion

a) Elastic 

A firecracker sits motionless on a sidewalk before exploding. Its pieces, which  have different masses, move away from the explosion site in all directions and high  velocities. The statements below compare the firecracker before the explosion to all  of the moving pieces just after the explosion. Select the statement that is most  accurate.  

a) The momentum of the firecracker is less than the sum of the momenta of all  the pieces. 

b) All of the pieces move away from the explosion site at the same velocity.

c) The momentum of the firecracker is equal to the sum of the momenta of its  pieces. 

d) The velocity of the firecracker is greater than the sum of the velocities of its pieces.

c) The momentum of the firecracker is equal to the sum of the momenta of its  pieces. 

Two students are roller-blading around the school. At one point, student 1 is  skating behind the other at a faster rate and cannot stop. How will their individual  velocities change after student 1 crashes into student 2?  

a) Their velocities will increase.  

b) Their velocities will decrease. 

c) Student 1 velocity will increase and student 2 velocity will decrease.

d) Student 1 velocity will decrease and student 2 velocity will increase.

d) Student 1 velocity will decrease and student 2 velocity will increase.

An object’s “quantity of motion” is equal to its…

momentum

Momentum is described as an object’s tendency to…

remain in motion

Impulse is the integral of the ___ _____ on an object over _____.

net force; time

Impulse is equal to a change in ________.

momentum

What is the center of mass?

The average position of all the mass in the system