Q: A ball is dropped from rest from a height of 20 m. Ignoring air resistance, what is its speed just before it hits the ground? (Use $$g = 9.8 \\ \mathrm{m/s^2$})$$

$$v = \\sqrt{2gh} = \\sqrt{2 \\times 9.8 \\times 20} = 19.8 \\ \mathrm{m/s}$$

Q: A 2 kg object moving at $$3 \\ \mathrm{m/s}$$ collides with a stationary 1 kg object in a perfectly inelastic collision. What is their final velocity?

$$v_f = \\frac{m_1$ v_1$ + m_2$ v_2$}{m_1$ + m_2$} = \\frac{2 \\times 3 + 1 \\times 0}{2 + 1} = 2 \\ \mathrm{m/s}$$

Q: A car accelerates from rest at $$2 \\ \mathrm{m/s^2$}$$ for 5 seconds. What is its final velocity?

$$v = v_0$ + at = 0 + 2 \\times 5 = 10 \\ \mathrm{m/s}$$

Q: A 0.5 kg ball is thrown vertically upward with an initial speed of $$8 \\ \mathrm{m/s}. $$What is its maximum height? (Use $$g = 9.8 \\ \mathrm{m/s^2$})$$

$$h = \\frac{v^2$}{2g} = \\frac{8^2$}{2 \\times 9.8} = 3.27 \\ \mathrm{m}$$

Q: A 3 kg object moving at $$4 \\ \mathrm{m/s}$$ has what kinetic energy?

$$KE = \\frac{1}{2}mv^2$ = \\frac{1}{2} \\times 3 \\times 4^2$ = 24 \\ \mathrm{J}$$

Q: A 5 kg box is pushed with a force of 20 N across a frictionless surface for 3 m. How much work is done on the box?

$$W = Fd = 20 \\times 3 = 60 \\ \mathrm{J}$$

Q: A 10 kg object falls freely from rest. What is its velocity after 2 seconds? (Use $$g = 9.8 \\ \mathrm{m/s^2$})$$

$$v = gt = 9.8 \\times 2 = 19.6 \\ \mathrm{m/s}$$

Question 1

A ball is dropped from rest from a height of 20 m. Ignoring air resistance, what is its speed just before it hits the ground? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 20} = 19.8 \ \mathrm{m/s}$$

Question 2

Which of the following best describes the difference between elastic and inelastic collisions?

Accepted Answer

Elastic collisions conserve both momentum and kinetic energy, while inelastic collisions conserve only momentum.

Question 3

A 2 kg object moving at $$3 \ \mathrm{m/s}$$ collides with a stationary 1 kg object in a perfectly inelastic collision. What is their final velocity?

Accepted Answer

$$v_f = \frac{m_1$ v_1$ + m_2$ v_2$}{m_1$ + m_2$} = \frac{2 \times 3 + 1 \times 0}{2 + 1} = 2 \ \mathrm{m/s}$$

Question 4

Which of the following is the correct expression for Newton's Second Law of Motion?

Accepted Answer

$$F = ma$$

Question 5

A car accelerates from rest at $$2 \ \mathrm{m/s^2$}$$ for 5 seconds. What is its final velocity?

Accepted Answer

$$v = v_0$ + at = 0 + 2 \times 5 = 10 \ \mathrm{m/s}$$

Question 6

Which of the following quantities is a scalar?

Accepted Answer

Speed

Question 7

A 0.5 kg ball is thrown vertically upward with an initial speed of $$8 \ \mathrm{m/s}. $$What is its maximum height? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$h = \frac{v^2$}{2g} = \frac{8^2$}{2 \times 9.8} = 3.27 \ \mathrm{m}$$

Question 8

Which of the following best describes the Law of Conservation of Momentum?

Accepted Answer

The total momentum of a closed system remains constant if no external forces act on it.

Question 9

A 3 kg object moving at $$4 \ \mathrm{m/s}$$ has what kinetic energy?

Accepted Answer

$$KE = \frac{1}{2}mv^2$ = \frac{1}{2} \times 3 \times 4^2$ = 24 \ \mathrm{J}$$

Question 10

Which formula gives the gravitational potential energy of an object of mass $$m at $$height $$h$$ above the ground?

Accepted Answer

$$U = mgh$$

Question 11

A 5 kg box is pushed with a force of 20 N across a frictionless surface for 3 m. How much work is done on the box?

Accepted Answer

$$W = Fd = 20 \times 3 = 60 \ \mathrm{J}$$

Question 12

Which of the following is true about static equilibrium?

Accepted Answer

The net force and net torque on the object are both zero.

Question 13

A 10 kg object falls freely from rest. What is its velocity after 2 seconds? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$v = gt = 9.8 \times 2 = 19.6 \ \mathrm{m/s}$$

Question 14

Which of the following is the correct SI unit for power?

Accepted Answer

Watt ($$\mathrm{W})$$

Question 15

A 0.2 kg ball moving at $$5 \ \mathrm{m/s}$$ strikes a wall and rebounds at $$-3 \ \mathrm{m/s}. $$What is the impulse delivered to the ball by the wall?

Accepted Answer

$$J = m(v_f - v_i) = 0.2 \times (-3 - 5) = -1.6 \ \mathrm{kg \cdot m/s}$$

Question 16

Which of the following best describes terminal velocity?

Accepted Answer

The constant speed reached when the force of gravity is balanced by air resistance.

Question 17

A 4 kg object is moving at $$6 \ \mathrm{m/s}$$ and comes to a stop in 2 seconds. What is the average force required to stop it?

Accepted Answer

$$F = \frac{m(v_f - v_i)}{t} = \frac{4 \times (0 - 6)}{2} = -12 \ \mathrm{N}$$

Question 18

Which of the following is the correct formula for acceleration?

Accepted Answer

$$a = \frac{v_f - v_i}{t}$$

Question 19

A 1.5 kg object is lifted to a height of 2 m. What is its gravitational potential energy? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$U = mgh = 1.5 \times 9.8 \times 2 = 29.4 \ \mathrm{J}$$

Question 20

Which of the following is NOT a vector quantity?

Accepted Answer

Mass

Fundamental Principles and Laws in Introductory Physics

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