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

Study Guide - Practice Questions

Study Guide - Flashcards