Q: A 2 kg object is dropped from a height of 10 m. Ignoring air resistance, what is its speed just before hitting the ground? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

$$v = \sqrt{2 g h} = \sqrt{2 \times 9.8 \times 10} \approx 14 \ \mathrm{m/s}$$

Q: A 0.5 kg ball is thrown straight up with an initial velocity of $$10 \ \mathrm{m/s}. $$What is the maximum height it reaches? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

$$h = \frac{v^2$}{2g} = \frac{10^2$}{2 \times 9.8} \approx 5.1 \ \mathrm{m}$$

Q: A 1000 kg car moving at $$20 \ \mathrm{m/s}$$ comes to a stop in 5 seconds. What is the magnitude of the average force applied to stop the car?

$$F = \frac{\Delta p}{\Delta t} = \frac{1000 \times 20}{5} = 4000 \ \mathrm{N}$$

Q: A 5 kg object is lifted vertically by 2 meters. What is the work done against gravity? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

$$W = m g h = 5 \times 9.8 \times 2 = 98 \ \mathrm{J}$$

Question 1

Which of the following best describes Newton's First Law of Motion?

Accepted Answer

An object at rest remains at rest, and an object in motion remains in motion at constant velocity unless acted upon by a net external force.

Question 2

A car of mass $$m$$ accelerates from rest under a constant force $$F$$ for a time $$t. $$What is the final velocity $$v of $$the car?

Accepted Answer

$$v = \frac{F t}{m}$$

Question 3

Which of the following is a correct statement of the Law of Universal Gravitation?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 4

A 2 kg object is dropped from a height of 10 m. Ignoring air resistance, what is its speed just before hitting the ground? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$v = \sqrt{2 g h} = \sqrt{2 	imes 9.8 	imes 10} \approx 14 \ \mathrm{m/s}$$

Question 5

Which of the following best explains why astronauts in the International Space Station appear weightless?

Accepted Answer

They are in continuous free fall around the Earth, experiencing apparent weightlessness.

Question 6

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

Accepted Answer

$$v = \sqrt{2 g h}$$

Question 7

A 0.5 kg ball is thrown straight up with an initial velocity of $$10 \ \mathrm{m/s}. $$What is the maximum height it reaches? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$h = \frac{v^2$}{2g} = \frac{10^2$}{2 	imes 9.8} \approx 5.1 \ \mathrm{m}$$

Question 8

Which of the following statements about impulse is correct?

Accepted Answer

Impulse is equal to the change in momentum of an object.

Question 9

A 1000 kg car moving at $$20 \ \mathrm{m/s}$$ comes to a stop in 5 seconds. What is the magnitude of the average force applied to stop the car?

Accepted Answer

$$F = \frac{\Delta p}{\Delta t} = \frac{1000 	imes 20}{5} = 4000 \ \mathrm{N}$$

Question 10

Which of the following best describes the concept of work in physics?

Accepted Answer

Work is the product of the force applied to an object and the displacement in the direction of the force.

Question 11

A 5 kg object is lifted vertically by 2 meters. What is the work done against gravity? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$W = m g h = 5 	imes 9.8 	imes 2 = 98 \ \mathrm{J}$$

Question 12

Which of the following is a correct statement of the conservation of energy principle?

Accepted Answer

The total energy of an isolated system remains constant.

Question 13

A 0.2 kg ball moving at $$15 \ \mathrm{m/s}$$ collides elastically with a stationary 0.2 kg ball. What is the velocity of the first ball after the collision?

Accepted Answer

$$0 \ \mathrm{m/s}$$

Question 14

A satellite orbits Earth in a circular path. Which force provides the necessary centripetal acceleration?

Accepted Answer

The gravitational force between the satellite and Earth.

Question 15

A 3 kg object moves in a circle of radius 2 m at a constant speed of $$4 \ \mathrm{m/s}. $$What is the magnitude of the centripetal force?

Accepted Answer

$$F = \frac{m v^2$}{r} = \frac{3 	imes 4^2$}{2} = 24 \ \mathrm{N}$$

Question 16

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is a measure of the amount of matter in an object, while weight is the force of gravity acting on that mass.

Question 17

A 10 kg box is pulled across a horizontal surface with a force of 50 N. If the coefficient of kinetic friction is 0.2, what is the acceleration of the box? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$a = \frac{F - \mu_k m g}{m} = \frac{50 - 0.2 	imes 10 	imes 9.8}{10} = \frac{50 - 19.6}{10} = 3.04 \ \mathrm{m/s^2$}$$

Question 18

Which of the following is an example of Newton's Third Law in action?

Accepted Answer

A swimmer pushes water backward, and the water pushes the swimmer forward.

Question 19

A 2 kg object is moving at $$5 \ \mathrm{m/s}. $$What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2} m v^2$ = \frac{1}{2} 	imes 2 	imes 25 = 25 \ \mathrm{J}$$

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