Quiz 03

A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain?

less than 30 J

A shell explodes into two fragments, one fragment 25 times heavier than the other. If any gas from the explosion has negligible mass, then

the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment

In an INELASTIC collision between two objects

the momentum of the system is conserved but the kinetic energy of the system is not conserved

A person carries a mass of 10 kg and walks along the +x-axis for a distance of 100 m with a constant velocity of 2 m/s. What is the work done by this person?

0 J

There must be equal amounts off mass on both side of the center of mass of an object

False

In a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?

Both objects receive the same impulse.

Which, if any of the following statements concerning the work done by a conservative force is NOT true?

None of these statements are true

A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?

The small car and the truck experience the same average force.

A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible. Case A: Thrown straight up Case B: Thrown straight down. Case C: Thrown out at an angle of 45 degrees Case D: Thrown straight out horizontally In which case will the speed of the stone be greatest when it hits the water below?

The speed will be the same in all cases.

Is it possible for a system to have negative potential energy?

Yes, since the choice of the zero of potential energy is arbitrary

Ibn a perfectly ELASTIC collision between two perfectly rigid objects

both the momentum and the kinetic energy of the system are conserved

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to MINIMIZE your speed on the skateboard?

catch the ball

If the net work done on an object is positive, then the object's kinetic energy

increases

A constant force is applied to an object. that causes a certain displacement. If the angle between the force and the displacement is 135 degree; the work done by this force is

negative

The plot in the figure shows the potential energy of a particle, due to the force exerted on it by another particle, as a function of distance. At which of the three points labeled in the figure is the magnitude of the force on the particle greatest?

point X

Two objects, one of mass m and the other of mass 2m, are dropped from the top of a building. When they hit the ground

the heavier one will have twice the kinetic energy of the lighter one

If a force always act perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy

true

Swimmers at a water park have a choice of two frictionless water slides as shown in the figure. Although both slides drop over the same height, h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v(1) of a swimmer reaching the end of slide 1 compares with v(2), the speed of a swimmer reaching the end of slide 2?

v(1) = v(2)

A simple pendulum, consisting of a mass m and string of length L, swings upward, making an angle theta with the vertical. The work done by the tension force is

zero

work done by STATIC FRICTION is always

zero