Newton's Laws of Motion

Question 1

What is Newton’s first law?

Answer 1

An object in motion will stay in motion unless acted upon by an unbalanced force, and an object at rest will stay at rest unless acted upon by an unbalanced force.

Question 2

What is Newton’s second law (equation)?

Answer 2

F=ma (Force= mass times acceleration)

Question 3

A ball is rolling along the ground, what force causes the ball to stop rolling?

Answer 3

friction

Question 4

Grab a piece of paper and use f=ma to figure out which of the following will result in the greatest acceleration.
a. 4 Newtons of force on a 10 kg object
b. 15 Newtons of force on a 3 kg object
c. 20 Newtons of force on a 2.5 kg object
d. 18 Newtons of force on a 5 kg object

Answer 4

c. f=ma
20=2.5a
20 divided by 2.5 equals 8.
8 m/s squared

Question 5

How could you find an objects center of mass?

Answer 5

You can try to balance the object on something, such as a yard stick or your fingers. You could also spin it in the air and see where the object appears to spin around. The point on which it balances or spins around is its center of mass.

Question 6

Where would the center of mass in a doughnut be?

Answer 6

In the middle of the hole.

Question 7

When riding a bike, the bike tire exerts a force on the ground, and the ground exerts a force on the bike tire. Which of the following statements is true?
a. The force that the tire exerts on the ground is greater than the force that the ground exerts on the tire which causes the bike to move forward
b. The force that the ground exerts on the tire is greater than the force that the tire exerts on the ground, which causes the bike to move forward.
c. The force of the tire on the ground and the ground on the tire are equal and in the same direction.
d. The force of the tire on the ground and the ground on the tire are equal but are in opposite directions

Answer 7

D. This is because of Newton’s third law of motion. Every action has an equal (in strength of force) and opposite (in direction) reaction.

Question 8

Grab a piece of paper. Draw a freebody diagram of a box sitting on a table. Be sure to include all of the forces acting on the box, and their relative strengths (using arrows)

Answer 8

Your drawing should be somewhat like this. You have a box sitting on a table. Your forces labeled are normal force, and gravity, whose arrows should be the same length.

Question 9

Grab a piece of paper. Draw a freebody diagram of a box that is being pushed across a table. Include all of the forces acting on the box, and their relative strengths (using arrows).

Answer 9

Your box should have normal force, gravity, friction, and push labeled. Be sure that the arrows for normal force and gravity are the same length.

Question 10

If a person throws a penny off of the empire state building, what forces are acting on it after it leaves the person’s hand?

Answer 10

Gravity and friction/air drag.

Question 11

You are standing on a skateboard that is at rest. Your friend (who is standing in front of the skateboard’s path) throws a heavy backpack at you, and you catch it. How will you move as a result of catching the backpack?

Answer 11

You will move backwards, but at a slower speed that the backpack was originally moving at.

Question 12

You and your friend are holding opposite ends of a rope. Your friend then pulls their end of the rope. Which person feels more force from the rope?

Answer 12

You both feel the same amount or strength of force, but in opposite directions. This is because of Newton’s third law.

Question 13

You are pushing a 10 kg box east with a force of 10N, while your friend pushes west with a force of 4N.
1. What is the net force acting on the box, and in what direction?
2. How quickly will the box accelerate, and in what direction. (Use F=ma.)

Answer 13

1. 6N east
   (10N-4N=6N)
2. 0.6 m/s² east.
   (F=ma or 6=10a so, 6 divided by 10, which equals 0.6.)