Question 1

A 70 kg astronaut is floating in deep space, far from any significant gravitational sources. She throws a 2 kg wrench away from her at 5 m/s. What is her velocity immediately after throwing the wrench?

Accepted Answer

$v = -0.14\ \mathrm{m/s}$

Question 2

Which of the following statements 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 3

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

Accepted Answer

$a = 1.04\ \mathrm{m/s^2}$

Question 4

A skier of mass 60 kg is sliding down a frictionless slope inclined at $30^\circ$ to the horizontal. What is the acceleration of the skier?

Accepted Answer

$a = 4.9\ \mathrm{m/s^2}$

Question 5

A 5 kg block is suspended by a rope. What is the tension in the rope if the block is being lowered at a constant velocity?

Accepted Answer

$T = 49\ \mathrm{N}$

Question 6

A 2 kg object is acted upon by two forces: $\vec{F}_1 = 3\ \mathrm{N}$ east and $\vec{F}_2 = 4\ \mathrm{N}$ north. What is the magnitude of the acceleration of the object?

Accepted Answer

$a = 2.5\ \mathrm{m/s^2}$

Question 7

A 1.0 kg object is on an incline of $25^\circ$. What is the component of the gravitational force acting down the incline?

Accepted Answer

$F = 4.1\ \mathrm{N}$

Question 8

A 0.5 kg ball is attached to a string and swung in a horizontal circle at constant speed. If the tension in the string is 10 N, what is the acceleration of the ball?

Accepted Answer

$a = 20\ \mathrm{m/s^2}$

Question 9

A 12 kg cart is pushed with a force of 30 N to the right while friction provides a force of 6 N to the left. What is the acceleration of the cart?

Accepted Answer

$a = 2.0\ \mathrm{m/s^2}$

Question 10

A 0.5 kg mass hangs from a light string. If the mass is accelerating upward at $2.0\ \mathrm{m/s^2}$, what is the tension in the string?

Accepted Answer

$T = 5.9\ \mathrm{N}$

Question 11

A 2 kg block and a 3 kg block are connected by a light string over a frictionless pulley (Atwood's machine). What is the acceleration of the system?

Accepted Answer

$a = 1.96\ \mathrm{m/s^2}$

Question 12

A 1.0 kg object is suspended from a spring scale in an elevator. If the elevator accelerates upward at $3.0\ \mathrm{m/s^2}$, what does the scale read?

Accepted Answer

$13\ \mathrm{N}$

Question 13

A 0.5 kg book rests on a table. What is the normal force exerted by the table on the book?

Accepted Answer

$N = 4.9\ \mathrm{N}$

Question 14

A 2 kg block is at rest on a frictionless incline of $30^\circ$. What is the magnitude of the normal force acting on the block?

Accepted Answer

$N = 16.97\ \mathrm{N}$

Question 15

A 1.5 kg object is pulled by a horizontal force of 10 N across a surface with friction force 4 N. What is the net acceleration?

Accepted Answer

$a = 2.67\ \mathrm{m/s^2}$

Question 16

A 0.5 kg mass is attached to a string and whirled in a vertical circle of radius 1.0 m. At the top of the circle, the speed is 4.0 m/s. What is the tension in the string at this point?

Accepted Answer

$T = 2.0\ \mathrm{N}$

Question 17

A 3 kg block is pulled up a $25^\circ$ incline with a force parallel to the incline. If the block moves at constant velocity, what is the magnitude of the pulling force?

Accepted Answer

$F = 12.4\ \mathrm{N}$

Question 18

A 1.0 kg object is suspended by two ropes at equal angles of $30^\circ$ from the vertical. What is the tension in each rope?

Accepted Answer

$T = 5.7\ \mathrm{N}$

Question 19

A 2 kg block is pushed against a wall with a horizontal force of 30 N. The coefficient of static friction between the block and the wall is 0.6. What is the maximum weight the friction can support before the block slides down?

Accepted Answer

$F_{\mathrm{max}} = 18\ \mathrm{N}$

Force and Motion I: Newton’s Laws – Dynamics, Forces, and Free-Body Diagrams

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