Question 1

Which of the following best explains why the Voyager space probe will continue its motion for billions of years?

Accepted Answer

There are no significant forces, such as friction, acting on it in space.

Question 2

A sled is sliding across a frictionless surface. What will happen to its motion if no additional forces act on it?

Accepted Answer

It will continue moving at a constant velocity.

Question 3

Which statement correctly describes a force?

Accepted Answer

A force is a push or a pull that acts on an object.

Question 4

Which of the following is a correct representation of a force vector?

Accepted Answer

The tail of the vector is placed on the object, and the arrow points in the direction of the force.

Question 5

Which of the following is NOT a contact force?

Accepted Answer

Weight (gravitational force)

Question 6

A box is being pulled by a rope, compressed by a spring, and is on Earth. Where should the tails of the force vectors be placed in a force diagram?

Accepted Answer

All tails should be placed on the particle representing the box.

Question 7

If the net force on an object points upward and two forces are shown as $$\vec{F}_1 ($$upward) and $$\vec{F}_2 ($$rightward), which direction must the third force $$\vec{F}_3$$ point?

Accepted Answer

Downward and to the left

Question 8

Which equation correctly expresses the relationship between acceleration $$a$$, force $$F$$, and mass $$m$$?

Accepted Answer

$$a = \frac{F}{m}$$

Question 9

A block is pulled with a constant force and its acceleration is measured to be $$3.0\,\mathrm{m/s^2$}. If $$another block is pulled with the same force and its acceleration is $$5.0\,\mathrm{m/s^2$}$$, what is the mass of the second block if the first block has a mass of $$1.0\,\mathrm{kg}$$?

Accepted Answer

$$0.60\,\mathrm{kg}$$

Question 10

Which force always acts perpendicular to the surface an object is pressing against?

Accepted Answer

Normal force

Question 11

Which force always acts parallel to the surface and opposes the motion of a sliding object?

Accepted Answer

Kinetic friction

Question 12

A skier is being towed up a snow-covered hill by a rope. Which forces act on the skier?

Accepted Answer

Tension, normal force, kinetic friction, and weight

Question 13

Which of the following is a long-range force?

Accepted Answer

Gravity

Question 14

If you double the mass of an object while keeping the force constant, what happens to its acceleration?

Accepted Answer

It is halved.

Question 15

Which of the following best describes the direction of the tension force exerted by a rope?

Accepted Answer

It is always in the direction of the rope.

Question 16

A bobsledder pushes her sled across horizontal snow and then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she jumps in?

Accepted Answer

Gravity, a normal force, and kinetic friction

Question 17

Which of the following is true about the acceleration of an object pulled with a constant force?

Accepted Answer

The acceleration is constant.

Question 18

Which force is responsible for the 'solidness' of solids?

Accepted Answer

Normal force

Question 19

Which of the following is the correct notation for the weight force vector?

Accepted Answer

$$\vec{w}$$

L7-8: Motion and Forces – Foundations of Force in Physics

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