Question 1

A 10 kg box is at rest on a horizontal surface. The coefficient of static friction between the box and the surface is 0.4. What is the minimum horizontal force required to start moving the box? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$39.2\ \mathrm{N}$$

Question 2

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

Accepted Answer

An object will remain at rest or move at constant velocity unless acted upon by a net external force.

Question 3

A 5 kg object is pulled by a horizontal force of $$20\ \mathrm{N} on a $$frictionless surface. What is its acceleration?

Accepted Answer

$$4\ \mathrm{m/s^2$}$$

Question 4

A 2 kg block is on an inclined plane at $$30^\circ to $$the horizontal. What is the component of the gravitational force acting down the incline? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$9.8\ \mathrm{N}$$

Question 5

A person of mass $$65\ \mathrm{kg}$$ stands on a scale in an elevator accelerating upward at $$2.0\ \mathrm{m/s^2$}. $$What does the scale read?

Accepted Answer

$$507\ \mathrm{N}$$

Question 6

Two blocks, $$m_1 = 3$$\ \mathrm{kg}$$ and m_2$ = 5\ \mathrm{kg}$$, are connected by a light string over a frictionless pulley. If $$m_2 is $$hanging and $$m_1 is on a $$frictionless table, what is the acceleration of the system? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$2.45\ \mathrm{m/s^2$}$$

Question 7

A 4 kg block slides down a frictionless incline of $$45^\circ. $$What is the normal force acting on the block? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$27.7\ \mathrm{N}$$

Question 8

Which of the following is NOT a correct statement of Newton's Third Law?

Accepted Answer

For every force, there is an equal and opposite force acting on the same object.

Question 9

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

Accepted Answer

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

Question 10

A 10 kg crate is pulled up a rough incline ($$	heta = 30^\circ) $$with a coefficient of kinetic friction $$\mu_k = 0.2. $$What is the net force parallel to the incline if the crate moves at constant velocity? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$0\ \mathrm{N}$$

Question 11

A 3 kg block is suspended by a rope. If the block is accelerating upward at $$2\ \mathrm{m/s^2$}$$, what is the tension in the rope? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$35.4\ \mathrm{N}$$

Question 12

Which of the following is a vector quantity?

Accepted Answer

Force

Question 13

A 2 kg block is pushed with a force of $$10\ \mathrm{N} at an $$angle of $$60^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$5.0\ \mathrm{N}$$

Question 14

A 1.5 kg object is moving at constant velocity on a horizontal surface. What is the net force acting on the object?

Accepted Answer

$$0\ \mathrm{N}$$

Question 15

A 6 kg block is pulled by a rope at an angle of $$30^\circ$$ above the horizontal with a tension of $$20\ \mathrm{N}. $$What is the horizontal component of the tension?

Accepted Answer

$$17.32\ \mathrm{N}$$

Question 16

A 5 kg block is on a frictionless table and is attached to a wall by a spring. If a force of $$15\ \mathrm{N} is $$applied and the block accelerates at $$2\ \mathrm{m/s^2$}$$, what is the force exerted by the spring?

Accepted Answer

$$10\ \mathrm{N}$$

Question 17

A 2 kg block is on a frictionless incline of $$60^\circ. $$What is the acceleration of the block down the incline? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$8.49\ \mathrm{m/s^2$}$$

Question 18

A 3 kg block is pulled by a force of $$12\ \mathrm{N} at an $$angle of $$0^\circ ($$horizontal) on a frictionless surface. What is the acceleration of the block?

Accepted Answer

$$4\ \mathrm{m/s^2$}$$

Question 19

A 2 kg block is acted on by two forces: $$\vec{F}_1 = 6\ \mathrm{N}$$ east and $$\vec{F}_2 = 8\ \mathrm{N}$$ north. What is the direction of the net force with respect to east?

Accepted Answer

$$53.1^\circ$$ north of east

Question 20

A 10 kg box is at rest on a horizontal surface. If a horizontal force of $$30\ \mathrm{N} is $$applied and the coefficient of kinetic friction is $$0.3$$, what is the acceleration of the box? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$0.14\ \mathrm{m/s^2$}$$

Physics I: Forces and Newton's Laws

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