Question 1

A 10 kg box rests on a horizontal surface. What is the magnitude of the normal force acting on the box?

Accepted Answer

$$98\ \mathrm{N}$$

Question 2

A 10 kg box is pushed downward with an additional force of $$20\ \mathrm{N}$$ while resting on a horizontal surface. What is the new normal force?

Accepted Answer

$$118\ \mathrm{N}$$

Question 3

A 10 kg box is pulled upward with a force of $$20\ \mathrm{N}$$ while resting on a horizontal surface. What is the normal force now?

Accepted Answer

$$78\ \mathrm{N}$$

Question 4

A $$80\ \mathrm{N}$$ box is pulled by a rope at $$20^\circ$$ above the horizontal with a tension of $$38\ \mathrm{N}. $$What is the vertical component of the tension?

Accepted Answer

$$13.00\ \mathrm{N}$$

Question 5

A $$3\ \mathrm{kg}$$ block is connected to a $$2\ \mathrm{kg}$$ block by a rope over a frictionless pulley. If the surface under the $$3\ \mathrm{kg}$$ block is frictionless, what is the acceleration of the system? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$3.92\ \mathrm{m/s^2$}$$

Question 6

A $$3\ \mathrm{kg}$$ block is on a table connected to a $$2\ \mathrm{kg}$$ hanging block by a rope over a pulley. If the coefficient of kinetic friction between the $$3\ \mathrm{kg}$$ block and the table is $$0.6$$, what is the frictional force acting on the $$3\ \mathrm{kg}$$ block?

Accepted Answer

$$17.64\ \mathrm{N}$$

Question 7

A $$4\ \mathrm{kg}$$ crate is pushed against a $$20\ \mathrm{kg}$$ crate with a force of $$36\ \mathrm{N}. $$What is the force exerted by the small crate on the big crate?

Accepted Answer

$$28.8\ \mathrm{N}$$

Question 8

A $$80\ \mathrm{N}$$ box is pulled by a rope at $$20^\circ$$ above the horizontal with a tension of $$38\ \mathrm{N}. $$What is the horizontal component of the tension?

Accepted Answer

$$35.71\ \mathrm{N}$$

Question 9

A $$275\ \mathrm{N}$$ bucket is being lifted upward with acceleration $$a. $$The tension at the bottom of the chain is $$T_{bottom}. $$Which equation correctly relates $$T_{bottom}$$, $$w_B$$, and $$a$$?

Accepted Answer

$$T_{bottom} = w_B + m_B a$$

Question 10

A $$125\ \mathrm{N}$$ chain is being lifted with acceleration $$a. $$What is the tension at the top of the chain?

Accepted Answer

$$T_{top} = w_C + m_C a$$

Question 11

A box of weight $$w is at $$rest on an inclined plane at angle $$	heta. $$What is the component of the weight parallel to the incline?

Accepted Answer

$$w \sin 	heta$$

Question 12

A box of weight $$w is at $$rest on an inclined plane at angle $$	heta. $$What is the component of the weight perpendicular to the incline?

Accepted Answer

$$w \cos 	heta$$

Question 13

A $$9800\ \mathrm{N}$$ box slides down a $$40^\circ$$ incline. What is the normal force acting on the box?

Accepted Answer

$$9800 \cos 40^\circ$$

Question 14

A person stands on a scale in an elevator accelerating upward. What does the scale read?

Accepted Answer

$$n = m(g + a)$$

Question 15

A box of weight $$w is at $$rest on a table. According to Newton's third law, what is the reaction force to the weight of the box?

Accepted Answer

The force of the box pulling the Earth upward with magnitude $$w$$

Question 16

A box is pulled by a rope at $$20^\circ$$ above the horizontal. What is the reaction force to the tension in the rope?

Accepted Answer

The force exerted by the box on the rope, equal in magnitude and opposite in direction to the tension

Question 17

A $$3\ \mathrm{kg}$$ block is on a table connected to a $$2\ \mathrm{kg}$$ hanging block by a rope over a pulley. If the coefficient of kinetic friction is $$0.6$$, what is the net force on the system?

Accepted Answer

$$1.96\ \mathrm{N}$$

Question 18

A $$2200\ \mathrm{N}$$ car engine is supported by three cables as shown. If the system is at rest, what is the vertical component of the tension $$T_3 in $$the cable at $$60^\circ$$?

Accepted Answer

$$T_3$$ \sin 60^\circ$$

Newton's Laws of Motion: Forces, Free-Body Diagrams, and Applications

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