Question 1

An object is in equilibrium. Which of the following statements must be true?

Accepted Answer

The object has zero acceleration.

Question 2

A 3-kg box is being lowered on a string at a constant speed. What is the tension in the string? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$29.4\ \mathrm{N}$$

Question 3

A loudspeaker is held in place by four vertical cables. The tension in each cable is $$30\ \mathrm{N}. $$What is the mass of the loudspeaker? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$3.06\ \mathrm{kg}$$

Question 4

Which of the following best describes the normal force ($$N) $$acting on an object resting on a horizontal surface?

Accepted Answer

It is always perpendicular to the surface.

Question 5

A 5 kg box is suspended in place by two cables at angles. What must be true for the box to remain in equilibrium?

Accepted Answer

The sum of the forces in the x-direction is zero, and the sum in the y-direction is zero.

Question 6

A chandelier is supported from the ceiling by two chains, each making a $$30^\circ$$ angle with the vertical. If the tension in each chain is $$50\ \mathrm{N}$$, what is the mass of the chandelier? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$8.8\ \mathrm{kg}$$

Question 7

A 2-kg box is dropped straight down from a building. A steady horizontal wind exerts a constant force of $$3\ \mathrm{N} on $$the box as it falls. What is the direction of the box's acceleration? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$8.7^\circ$$ below horizontal

Question 8

The Mars Rover Perseverance weighed about $$10,000\ \mathrm{N} on $$Earth and $$3,790\ \mathrm{N} on $$Mars. What is the gravitational acceleration on Mars?

Accepted Answer

$$3.7\ \mathrm{m/s^2$}$$

Question 9

A 3-kg bucket is being pulled upwards by a cord. The tension in the cord is $$35\ \mathrm{N}. $$What is the acceleration of the bucket? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$1.9\ \mathrm{m/s^2$}$$

Question 10

A 10-kg box moves on a flat surface at $$2\ \mathrm{m/s}. $$The coefficient of kinetic friction between the box and the surface is $$0.4. $$What is the kinetic friction force acting on the box? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$39\ \mathrm{N}$$

Question 11

You push a 3-kg box to give it an initial speed of $$5\ \mathrm{m/s}$$ across a floor. If $$\mu_k = 0.3$$, how far does the box travel before coming to a stop? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$7.7\ \mathrm{m}$$

Question 12

A 5.1 kg block is at rest on the floor. The coefficients of static and kinetic friction are $$\mu_s = 0.7$$ and $$\mu_k = 0.5. $$Calculate the force needed to get the block moving, and the force needed to keep it moving at constant speed. Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$F = 35\ \mathrm{N};\ F = 25\ \mathrm{N}$$

Question 13

A 20 kg block on a horizontal, frictionless surface is pushed and accelerates to $$30\ \mathrm{m/s}$$ from rest in $$6\ \mathrm{s}. $$What is the magnitude of the applied force exerted on the block?

Accepted Answer

$$100\ \mathrm{N}$$

Question 14

An 800-kg car is traveling at $$20\ \mathrm{m/s}$$ and comes to a stop due to a $$5,000\ \mathrm{N}$$ net force. How far did the car travel while stopping?

Accepted Answer

$$64\ \mathrm{m}$$

Question 15

A 1000-kg rocket is taking off from rest. The force of gravity is $$10,000\ \mathrm{N} ($$down), the engines provide $$25,000\ \mathrm{N} (up$$), and air resistance is $$5,000\ \mathrm{N} ($$down). What is the rocket's velocity after $$20\ \mathrm{s}$$?

Accepted Answer

$$200\ \mathrm{m/s}$$

Question 16

Which of the following statements about static and kinetic friction is correct?

Accepted Answer

The coefficient of static friction is always greater than or equal to the coefficient of kinetic friction.

Dynamics I: Motion Along a Line – Comprehensive Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards