Q: A block of mass $$m is $$pulled by a force $$F at an $$angle $$\theta$$ above the horizontal. What are the $$x$$ and $$y$$ components of the force?

$$F_x = F \cos \theta$$, $$F_y = F \sin \theta$$

Question 1

Which of the following best describes the direction of the normal force $$\vec{n}$$ acting on an object resting on a surface?

Accepted Answer

Perpendicular to the surface

Question 2

A block of mass $$m is $$sliding down an inclined plane at angle $$\alpha$$ with friction force $$F. $$What is the magnitude of the normal force $$N$$ exerted by the plane on the block?

Accepted Answer

$$N = mg \cos \alpha$$

Question 3

Which of the following statements about friction force $$\vec{f} is $$correct?

Accepted Answer

It acts parallel to the surface and opposes sliding.

Question 4

A 10-N force is applied at 30° above the horizontal to a box on a frictionless surface. What is the horizontal component of the force?

Accepted Answer

$$10 \cos 30^\circ$$

Question 5

Two forces $$\vec{F}_1$$ and $$\vec{F}_2$$ act on a body at point $$O. $$What is the net effect of these forces?

Accepted Answer

The body experiences a force equal to their vector sum $$\vec{R}.$$

Question 6

A puck slides on an air-hockey table with negligible friction. According to Newton's First Law, what will happen to the puck?

Accepted Answer

It will continue moving at constant velocity.

Question 7

In a tug-of-war, if $$\vec{F}_1 = -\vec{F}_2$$, what is the net force on the rope?

Accepted Answer

$$\vec{F}_1 + \vec{F}_2 = 0$$

Question 8

A block of mass $$m is $$pulled by a force $$F at an $$angle $$	heta$$ above the horizontal. What are the $$x$$ and $$y$$ components of the force?

Accepted Answer

$$F_x = F \cos 	heta$$, $$F_y = F \sin 	heta$$

Question 9

A 5 kg object is acted on by a net force of 20 N. What is its acceleration?

Accepted Answer

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

Question 10

A block of mass $$m$$ slides down a frictionless incline at angle $$\alpha. $$What is its acceleration?

Accepted Answer

$$a = g \sin \alpha$$

Question 11

A 60 kg astronaut floats inside the International Space Station. What is the magnitude of the net force acting on the astronaut?

Accepted Answer

$$0$$

Question 12

A block of mass $$m is $$sliding down an incline with friction force $$F. $$What is the acceleration of the block?

Accepted Answer

$$a = g \sin \alpha - \frac{F}{m}$$

Question 13

A block is suspended by two ropes at equal angles $$\alpha to $$the horizontal. What is the tension $$T in $$each rope?

Accepted Answer

$$T = \frac{mg}{2 \sin \alpha}$$

Question 14

A 10-tonne capsule on the London Eye (diameter 120 m, period 30 min) experiences what net force at the bottom of the wheel?

Accepted Answer

$$7.3\ \mathrm{N}$$

Question 15

Which of the following is NOT a contact force?

Accepted Answer

Gravitational force

Question 16

A child and parent parachute jump together and reach terminal velocity. How do the magnitudes of the net forces on them compare?

Accepted Answer

Both experience zero net force.

Question 17

Which of the following is true about mass and weight?

Accepted Answer

Weight is a vector, mass is a scalar.

Question 18

A block of mass $$m is at $$rest on a horizontal surface. Which forces act on the block?

Accepted Answer

Weight and normal force

Forces and Newton's Laws: Foundations of Dynamics

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