physics 101 lesson 4

The momentum change of an object is equal to the force acting on the object. velocity change of the object. impulse acting on the object. mass of the object times the force acting on it.

impulse acting on the object

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 it increases the impact time. decreases the impulse on the glove. decreases the change in momentum of the ball. all of the above.

increases the impact time.

Work is equal to the product of velocity and time. mass and acceleration. force and time. force and distance.

force and distance.

The formula for kinetic energy is KE equals ____. mv ½ mv2 ma mgh

½ mv2

The work done against gravity in moving a box with a weight of 20 newtons through a height of 5 meters is 100 newtons. 100 joules. 1000 joules. 4 joules. 1000 newtons.

100 joules. ----- the force of gravity vs. lifting cancels the g out in the formula mgh so it would just be mh.

A 5,000-kg freight car runs into a 10,000-kg freight car at rest. They couple (stick together) upon collision and move with a speed of 2 m/s. What was the initial speed of the 5,000-kg car? 8 m/s 4 m/s 5 m/s 6 m/s

6 m/s

Which of the following is true? A body with zero velocity cannot have any potential energy. A body with zero acceleration cannot have any kinetic energy. A body with zero acceleration cannot have any potential energy. A body with zero velocity cannot have any kinetic energy.

A body with zero velocity cannot have any kinetic energy.

Which of these is the most accurate statement about momentum in a collision between two objects? Momentum is only conserved if the colliding objects bounce apart. Momentum is only conserved if the collision is elastic. Momentum is never conserved. Momentum is always conserved.

Momentum is always conserved.

The unit of energy is the joule, which is equal to a kg-m. kg/s. N-m/s. N-m.

N-m.

he formula for gravitational potential energy is PE equals ____. mgh ma ½ mv2 Fd

mgh

Impulse is equal to the change in ____ of the object on which the impulse acts. force acceleration velocity momentum

momentum

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the force against the rifle is small compared to the force on the bullet. speed is mainly concentrated in the bullet. rifle has significantly greater mass compared to the bullet. momentum of the rifle is unchanged.

rifle has significantly greater mass compared to the bullet.

A freight car moving at 20 m/s to the right strikes a stationary freight car of the same mass. If the collision is elastic, the first car will move left, and the second car will move right, both at 10 m/s. the first car will stop, and the second car will move away at 20 m/s to the right. both cars will move together to the right at 10 m/s. the first car will move left, and the second car will move right, both at 20 m/s.

the first car will stop, and the second car will move away at 20 m/s to the right.

The SI unit for power is the joule. kg-m/s. watt. kg-m/s2.

watt.

When you run up two flights of stairs instead of walking up them, you feel more tired because your power output is greater when you run than when you walk. a running person has more inertia than a walking person. you do more work when you run than when you walk. the gravitational force is greater on a running person than on a walking person.

your power output is greater when you run than when you walk.