Q: A 1500 kg car traveling at 12 m/s suddenly runs out of gas while approaching a valley. What will be the car's speed as it coasts into the gas station on the other side of the valley, assuming no friction?

The same as its initial speed, $$12\ \text{m/s}$$

Question 1

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____.

Accepted Answer

the same magnitude and sign

Question 2

A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____.

Accepted Answer

negative

Question 3

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____.

Accepted Answer

the object's speed did not change

Question 4

The kinetic energy of an object depends on its mass and speed. Which of the following sets of objects has the greatest total kinetic energy?

Accepted Answer

Two cantaloupes, total mass 4 kg, speed 2 m/s

Question 5

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with a 12 N force, directed at an angle of $$15^	ext{o}$$ above the ground. How much work does Max do on the sled as he pulls it 25 m in the snow?

Accepted Answer

$$77.8\ 	ext{J}$$

Question 6

A block of mass $$m$$ slides down a frictionless incline of height $$h. $$What is its speed at the bottom?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 7

The work-energy theorem states that the net work done by all forces acting on an object is equal to the change in ____ energy.

Accepted Answer

kinetic

Question 8

To calculate the change in kinetic energy, you must know the force as a function of ____.

Accepted Answer

position

Question 9

A 1500 kg car traveling at 12 m/s suddenly runs out of gas while approaching a valley. What will be the car's speed as it coasts into the gas station on the other side of the valley, assuming no friction?

Accepted Answer

The same as its initial speed, $$12\ 	ext{m/s}$$

Question 10

Which of the following best describes the energy transformation when a sled slides down a hill and comes to rest due to friction?

Accepted Answer

$$K_i + U_i = K_f + U_f + \Delta E_{th}$$

Question 11

The gravitational potential energy of an object near Earth's surface is given by ____.

Accepted Answer

$$U_g = mgh$$

Question 12

If only conservative forces act on a system, the total mechanical energy is ____.

Accepted Answer

conserved

Question 13

A particle of mass $$m$$ moves in the x-direction under a constant acceleration $$a. $$What is the work done by the net force as the particle moves from $$x_1 to$$ $$x_2$$?

Accepted Answer

$$W = m a (x_2$ - x_1$)$$

Question 14

The work done by a variable force $$F(x) as a $$particle moves from $$x_1 to$$ $$x_2 is $$given by ____.

Accepted Answer

$$W = \int_{x_1$}^{x_2$} F(x) dx$$

Question 15

A block slides down a frictionless ramp and then across a rough horizontal surface, coming to rest. Which energy transformation occurs?

Accepted Answer

Potential energy is converted to kinetic energy, then to thermal energy

Question 16

Which word in the statement of a problem assures you that the table is frictionless?

Accepted Answer

smooth

Question 17

The kinetic energy of a system is always ____ if the mass and velocity are given.

Accepted Answer

positive

Question 18

If nonconservative forces such as friction act within a system, the total mechanical energy will ____.

Accepted Answer

decrease

Question 19

A spring with spring constant $$k is $$compressed by a distance $$x. $$What is the elastic potential energy stored in the spring?

Accepted Answer

$$U_e = \frac{1}{2}kx^2$

Question 20

A ball of mass $$m is $$dropped from height $$h$$ and lands with speed $$v. $$Ignoring air resistance, which equation expresses conservation of energy?

Accepted Answer

$$mgh = \frac{1}{2}mv^2$

Work, Kinetic Energy, and Potential Energy: Principles and Applications

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