Q: A 10 kg box is at rest on a horizontal frictionless surface. Two forces act on it: $$\vec{F}_1 = 15\,\mathrm{N} to $$the right and $$\vec{F}_2 = 10\,\mathrm{N} to $$the left. What is the acceleration of the box?

$$a = 2.5\,\mathrm{m/s^2$}$$\,\text{to the right}$

Q: A $$65\,\mathrm{kg}$$ skier descends a frictionless slope inclined at $$32^\circ. $$What is the component of the skier's weight parallel to the slope?

$$65 \times 9.8 \times \sin 32^\circ$$

Question 1

A 10 kg box is at rest on a horizontal frictionless surface. Two forces act on it: $$\vec{F}_1 = 15\,\mathrm{N} to $$the right and $$\vec{F}_2 = 10\,\mathrm{N} to $$the left. What is the acceleration of the box?

Accepted Answer

$$a = 2.5\,\mathrm{m/s^2$}$$\,	ext{to the right}$

Question 2

A person stands on a scale in an elevator that is accelerating upward at $$2.0\,\mathrm{m/s^2$}. If $$the person's mass is $$70\,\mathrm{kg}$$, what does the scale read?

Accepted Answer

$$826\,\mathrm{N}$$

Question 3

A block of mass $$m is $$pulled by a rope at an angle $$	heta$$ above the horizontal with tension $$T. $$What is the vertical component of the tension force?

Accepted Answer

$$T \sin 	heta$$

Question 4

A $$5.0\,\mathrm{kg}$$ object is acted upon by two forces: $$\vec{F}_1 = 8\,\mathrm{N}$$ east and $$\vec{F}_2 = 6\,\mathrm{N}$$ north. What is the magnitude of the object's acceleration?

Accepted Answer

$$2.0\,\mathrm{m/s^2$}$$

Question 5

A $$40\,\mathrm{kg}$$ box is pushed with a constant force of $$20\,\mathrm{N} on a $$level surface with friction. If the box moves at constant velocity, what is the magnitude of the friction force?

Accepted Answer

$$20\,\mathrm{N}$$

Question 6

A $$0.5\,\mathrm{kg}$$ ketchup bottle slides on a countertop and comes to rest after traveling $$1.0\,\mathrm{m}$$ from an initial speed of $$2.0\,\mathrm{m/s}. $$What is the magnitude of the friction force acting on the bottle?

Accepted Answer

$$1.0\,\mathrm{N}$$

Question 7

A $$65\,\mathrm{kg}$$ skier descends a frictionless slope inclined at $$32^\circ. $$What is the component of the skier's weight parallel to the slope?

Accepted Answer

$$65 	imes 9.8 	imes \sin 32^\circ$$

Question 8

Which of the following statements about Newton's third law is correct?

Accepted Answer

Action-reaction pairs are equal in magnitude and opposite in direction.

Question 9

A $$6.00\,\mathrm{kg}$$ crate and a $$4.00\,\mathrm{kg}$$ crate are connected by a rope and pulled with a $$20\,\mathrm{N}$$ force. Ignoring friction, what is the acceleration of the system?

Accepted Answer

$$2.0\,\mathrm{m/s^2$}$$

Question 10

A block is lifted at constant speed by a cable. Which statement is true about the forces acting on the block?

Accepted Answer

The tension in the cable equals the weight of the block.

Question 11

A $$50\,\mathrm{kg}$$ person stands on a scale in an elevator that is in free fall. What does the scale read?

Accepted Answer

$$0\,\mathrm{N}$$

Question 12

A $$10\,\mathrm{N}$$ force is applied at $$30^\circ$$ above the horizontal. What are the $$x$$ and $$y$$ components of the force?

Accepted Answer

$$F_x = 10 \cos 30^\circ$$, $$F_y = 10 \sin 30^\circ$$

Question 13

A $$2.00\,\mathrm{kg}$$ block is accelerated upward at $$3.00\,\mathrm{m/s^2$}. $$What is the magnitude of the upward force exerted on the block?

Accepted Answer

$$25.6\,\mathrm{N}$$

Question 14

A $$10\,\mathrm{kg}$$ object is acted upon by a net force of $$30\,\mathrm{N} at$$ $$60^\circ$$ above the horizontal. What is the magnitude of the acceleration?

Accepted Answer

$$3.0\,\mathrm{m/s^2$}$$

Question 15

A $$5.0\,\mathrm{kg}$$ object is pulled by two ropes: one exerts $$12\,\mathrm{N} at$$ $$0^\circ$$ and the other $$16\,\mathrm{N} at$$ $$90^\circ. $$What is the magnitude of the net force?

Accepted Answer

$$20\,\mathrm{N}$$

Question 16

A $$10\,\mathrm{kg}$$ box is at rest on a horizontal surface. What is the normal force exerted by the surface?

Accepted Answer

$$98\,\mathrm{N}$$

Question 17

A $$2.0\,\mathrm{kg}$$ block is pulled by a $$10\,\mathrm{N}$$ force at $$45^\circ$$ above the horizontal. What is the vertical component of the force?

Accepted Answer

$$10 \sin 45^\circ$$

Question 18

A $$5.0\,\mathrm{kg}$$ object is acted upon by a net force of $$15\,\mathrm{N} to $$the right. What is the acceleration?

Accepted Answer

$$3.0\,\mathrm{m/s^2$}$$

Newton's Laws of Motion and Forces: Study Notes

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