Q: A force $$F$$ acts at an angle $$\theta$$ above the horizontal. What are the $$x$$ and $$y$$ components of $$F$$?

$$F \cos \theta, F \sin \theta$$

Q: A 12 kg dog slides down a slide at $$55^\circ$$ with a coefficient of kinetic friction $$\mu_k = 0.45. $$Which equation describes the application of Newton's 2nd law in the $$x-$$direction?

$$mg \sin \theta - f_k = +ma_x$$

Q: For a car turning on a frictionless banked road (see images 4 and 5), which equation describes the motion along the radial direction ($$r$$)?

$$n \sin \theta = \frac{mv^2$}{r}$$

Question 1

Two communications satellites are in orbit at the same height, but one has twice the mass of the other. What can you say about the speed of the heavier satellite compared to the lighter one?

Accepted Answer

Both satellites move at the same speed.

Question 2

A position vs. time graph shows an object moving from position $$x = 10\ \mathrm{m} at$$ $$t = 4\ \mathrm{s} to$$ $$x = 16\ \mathrm{m} at$$ $$t = 10\ \mathrm{s}. $$What is the average velocity between $$4\ \mathrm{s}$$ and $$10\ \mathrm{s}$$?

Accepted Answer

$$\frac{5}{6}\ \mathrm{m/s}$$

Question 3

How do you determine the acceleration from a velocity vs. time graph?

Accepted Answer

By finding the slope of the graph

Question 4

Refer to the acceleration vs. time graph (first image). If positive acceleration is east, which best describes the motion shown?

Accepted Answer

Moving west and speeding up

Question 5

A ball is dropped from rest and falls $$56\ \mathrm{m} to $$the ground. Which kinematic equation is best to find the time it takes to hit the ground?

Accepted Answer

$$\Delta y = v_{iy} t + \frac{1}{2} a_y t^2$

Question 6

Two objects, one with mass $$3m$$ and one with mass $$m$$, collide. Which exerts more force during the collision?

Accepted Answer

Both exert the same force on each other

Question 7

A sailboat is moving to the right at a constant velocity across the sea. What is the direction of the net force on the boat?

Accepted Answer

Net force is zero

Question 8

An object slides downhill. Which set of forces is correct? (P = normal, Q = none, R = friction, S = none, T = weight)

Accepted Answer

P = normal, Q = none, R = friction, S = none, T = weight

Question 9

A force $$F$$ acts at an angle $$	heta$$ above the horizontal. What are the $$x$$ and $$y$$ components of $$F$$?

Accepted Answer

$$F \cos 	heta, F \sin 	heta$$

Question 10

A pendulum ball is at an angle $$	heta$$ with the vertical. Which equation best describes equilibrium along the $$y-$$direction?

Accepted Answer

$$T \cos 	heta - mg = 0$$

Question 11

A 12 kg dog slides down a slide at $$55^\circ$$ with a coefficient of kinetic friction $$\mu_k = 0.45. $$Which equation describes the application of Newton's 2nd law in the $$x-$$direction?

Accepted Answer

$$mg \sin 	heta - f_k = +ma_x$$

Question 12

A car drives through the bottom of a round valley while speeding up. What is the direction of the acceleration at the lowest point?

Accepted Answer

Upward and forward

Question 13

For a car turning on a frictionless banked road (see images 4 and 5), which equation describes the motion along the radial direction ($$r$$)?

Accepted Answer

$$n \sin 	heta = \frac{mv^2$}{r}$$

Question 14

According to Newton's law of universal gravitation, what happens to the gravitational force if the distance between two masses is reduced by half?

Accepted Answer

It becomes four times larger compared to the original.

Question 15

A truck is turning on a banked curve (see image 5). If the friction is neglected, what force provides the necessary centripetal acceleration?

Accepted Answer

The horizontal component of the normal force

Question 16

In circular motion (see image 3), what is the direction of the acceleration vector at any instant?

Accepted Answer

Toward the center of the circle

Question 17

A satellite orbits Earth at a constant speed. Which of the following statements is true about the net force acting on the satellite?

Accepted Answer

The net force is directed toward the center of the Earth.

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