# Physics: Momentum Chp 7

Flashcard maker : Lily Taylor
The momentum of an object is defined as the object’s
mass times its velocity
Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?
The large truck
Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has
twice as much momentum
If the momentum of an object changes and its mass remains constant
all of the above (it is accelerating or decelerating, there is a force acting on it, its velocity id changing)
The momentum change of an object is equal to the
impulse acting on it
In order to increase the final momentum of a gold ball, we could
all of the above (increase the force acting on it, follow through when hitting the ball, increase the time of contact with the ball, swing as hard as possible)
The reason padded dashboards are used in cars is that they
increase the time of impact in a collision
A table tennis ball launcher is fired. Compared to the force on the ball, the force on the launcher is
the same
A table tennis ball launcher is fired. Compared to the impulse on the ball, the force on the launcher is
the same
Momentum of a system is conserved only when
there is no net external force acting on the system
A collision is considered elastic if
all of the above (there is no lasting deformation, the objects don’t stick together, the objects that collide don’t get warmer, after the collision the objects have the same shape as before the collision)
Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice, she can
throw something in the direction opposite to the way she wants to go
Which of the following has the largest momentum?
A pickup truck traveling down the highway
A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, its momentum would be
doubled
A cannon recoils from launching a cannonball. The speed of the cannon’s recoil is small because the
cannon has far more mass than the cannonball
Suppose a cannon is made of a strong but very light material. Suppose also that the cannonball is more massive than the cannon itself. For such a system
the target would be a safer place than where the operator is located
Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has a higher
momentum
In order to catch a ball, a baseball player moves his or her hand backward in the direction of the ball’s motion. Doing this reduces the force of impact on the player’s hand principally because
the time of impact is increased
A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has
all of the above (less stopping distance, more momentum, more mass)
A cannon fires a cannonball. The speed of the cannonball will be the same as the speed of the recoiling cannon
if the mass of the cannonball equals the mass of the cannon
The force of an apple hitting the ground depends upon
all of the above (the speed of the apple just before it hits, the time of impact with the ground, whether or not the apple bounces, air resistance on the apple as it falls)
When you jump off a step, you usually bend your knees as you reach the ground. By doing this, the time of the impact is about 10 times more what it would be in a stiff-legged landing, and the average force on your body is reduced by
Recoil is noticeable if you throw a heavy ball while standing on roller skates. If instead you go through the motions of throwing the ball but hold onto it, your net recoil velocity will be
zero
A 1 N apple falls to the ground. The apple hits the ground with an impact force of
1 N
A karate expert executes a swift blow and splits a cement block with her bare hand.
all of the above (the forces on both the block and the expert’s hand have the same magnitude, the times of impact on both the block and the expert’s and are the same
A moving freight car runs into an identical car at rest on the track. The cars couple together. Compared to the velocity of the first car before the collision, the velocity of the combined cars after the collision is
one half as large
Two gliders having the same mass and speed move toward each other on an air track and stick together. After the collision, the velocity of the gliders is
zero
A piece of putty moving with 2 units of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both are set in motion with a combined momentum that is
2 units
The force that accelerates a rocket into outer space is exerted on the rocket by
the exhaust gases
If all people, animals, trains and trucks all over the world began to walk or run towards the east, then
Earth would spin a bit slower
Suppose an astronaut in outer space wishes to toss a ball against a very massive and perfectly elastic concrete wall and catch it as it bounces back. If the ball is as massive as the astronaut, then
the astronaut will never catch the first bounce
A table tennis ball moving forward with 5 units of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball that is set in motion with a momentum of
more than 5 units
Superman is at rest in space when he throws an asteroid that has more mass than he does. Which moves faster, Superman or the asteroid?
Superman
A cannonball shot from a long-barrel cannon travels faster than one shot from a short-barrel cannon because the cannonball receives a greater
impulse
While roller-skating, Granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction effects, Ambroses’s speed after the collision will be greatest when
he and Granny make a bouncing collision, each going in opposite direction
A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives the greater impulse is the
limousine
A 2 kg ball is thrown at 3 m/s. What is the ball’s momentum?
6 kg m/s
A 4.0 kg ball has a momentum of 20.0 kg m/s. What is the ball’s speed?
5.0 m/s
A ball is moving at 6.0 m/s and has a momentum of 24.0 kg m/s . What is the ball’s mass?
4.0 kg
A 5.0 kg chunk of putty moving at 10.0 m/s collides with and sticks to a 7.0 kg bowling ball that is initially at rest. The bowling ball with its putty passenger will then be set in motion with a momentum of
50.0 kg m/s