Q: A 10 kg object is lifted to a height of 5 meters above the ground. What is its gravitational potential energy? (Use $$g = 9.8 \text{ m/s}^2)$$

$$PE = 10 \times 9.8 \times 5 = 490 \text{ J}$$

Q: A 2 kg object is moving at 3 m/s. What is its kinetic energy?

$$KE = \frac{1}{2} \times 2 \times 3^2$ = 9 \text{ J}$$

Q: A car of mass 1000 kg is accelerated from rest to a speed of 20 m/s. What is the work done on the car?

$$W = \frac{1}{2} \times 1000 \times 20^2$ = 200,000 \text{ J}$$

Question 1

A ball is tossed in the air and caught at the same height from which it was thrown. Neglecting air resistance, which of Newton's laws best explains why the ball continues moving upward after it leaves the thrower's hand?

Accepted Answer

Newton's 1st Law: Inertia

Question 2

A rocket launches vertically from Earth. Which statement best describes the forces involved according to Newton's Third Law?

Accepted Answer

The rocket pushes exhaust gases downward, and the gases push the rocket upward.

Question 3

A 10 kg object is lifted to a height of 5 meters above the ground. What is its gravitational potential energy? (Use $$g = 9.8 	ext{ m/s}^2)$$

Accepted Answer

$$PE = 10 	imes 9.8 	imes 5 = 490 	ext{ J}$$

Question 4

Which scenario best illustrates Newton's Third Law in everyday life?

Accepted Answer

A swimmer moves forward by pushing water backward.

Question 5

A balloon helicopter rises when air rushes out of the balloon and spins the blades. What is the primary force that lifts the helicopter?

Accepted Answer

The downward push of the blades on the air, resulting in an equal and opposite upward force on the blades (Newton's 3rd Law).

Question 6

A 2 kg object is moving at 3 m/s. What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2} 	imes 2 	imes 3^2$ = 9 	ext{ J}$$

Question 7

In the PhET Energy Skate Park simulation, where does the skater have the maximum kinetic energy?

Accepted Answer

At the bottom of the hill

Question 8

If the speed of an object is doubled, by what factor does its kinetic energy increase?

Accepted Answer

It quadruples

Question 9

A lever allows a small force over a large distance to induce a large force over a short distance. What is the main advantage of using a lever?

Accepted Answer

It multiplies the input force.

Question 10

A car of mass 1000 kg is accelerated from rest to a speed of 20 m/s. What is the work done on the car?

Accepted Answer

$$W = \frac{1}{2} 	imes 1000 	imes 20^2$ = 200,000 	ext{ J}$$

Question 11

Which of the following best describes the work-energy theorem?

Accepted Answer

Any change in kinetic energy is the result of work: $$W = \Delta KE$$

Question 12

A pile driver drops a heavy weight onto a post, driving it into the ground. Which energy transformation occurs during this process?

Accepted Answer

Potential energy to kinetic energy

Question 13

Which of the following is NOT a source of energy mentioned in the study materials?

Accepted Answer

Magnetism

Question 14

A pulley system allows a load to be lifted with an input force half the weight of the load. What is the mechanical advantage of this system?

Accepted Answer

2

Question 15

Which statement about energy is correct according to the study materials?

Accepted Answer

Energy is a conserved quantity and can be transformed but not destroyed.

Question 16

A skater at the top of a hill in the Energy Skate Park simulation has maximum potential energy. What happens to this energy as the skater moves down the hill?

Accepted Answer

It is transformed into kinetic energy.

Question 17

Which of the following best explains why a balloon stays in place before its nozzle is opened?

Accepted Answer

The forces inside the balloon are balanced and cancel each other out.

Question 18

Which process is an example of recycled energy as described in the study materials?

Accepted Answer

Using heat from a power plant to warm buildings.

Question 19

A person applies the brakes to a moving car, bringing it to a stop. According to the work-energy theorem, what does the work done by the brakes equal?

Accepted Answer

The car's change in kinetic energy

Question 20

Which of the following statements about the relationship between kinetic energy and speed is correct?

Accepted Answer

Kinetic energy increases with the square of speed: $$KE = \frac{1}{2}mv^2$

Newton's Laws and Energy: Foundations of Mechanics

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