Question

1. if you push a skateboard and it rolls forward, which law explains why it moves?

a) newton’s first law
b) newton’s second law
c) newton’s third law
d) law of gravity

1. what happens to the momentum of an object if its mass doubles but its velocity stays the same?

a) the momentum doubles
b) the momentum stays the same
c) the momentum is cut in half
d) the momentum becomes zero

1. what does pressure measure?

a) mass per unit volume
b) the amount of force applied per unit area
c) the speed of an object
d) the direction of a force

calculation questions: show your work for each problem.

1. calculate the weight of a 3 kg object on earth. (use g = 9.8 m/s²)

weight = ______ n

1. a runner travels 100 meters in 20 seconds. what is her velocity?

velocity = ______ m/s

1. a car speeds up from 10 m/s to 30 m/s in 5 seconds. what is its acceleration?

acceleration = ______ m/s²

1. a box with a force of 200 n is placed on a table with an area of 2 m². what is the pressure on the table?

pressure = ______ pa

1. what is the momentum of a 2 kg ball moving at 4 m/s?

momentum = ______ kg·m/s

Explanation:

Multiple - Choice Questions

Question 3

Newton's Second Law ($F = ma$) states that a force causes an acceleration (change in motion). Pushing the skateboard applies a force, causing it to move. Newton's First Law is about inertia (objects at rest or in motion stay that way without force), Third Law is action - reaction, and Law of Gravity is about gravitational force. So the correct law is Newton's Second Law.

The formula for momentum is $p=mv$. If mass ($m$) doubles and velocity ($v$) stays the same, then the new momentum $p'=(2m)v = 2mv=2p$. So the momentum doubles.

Pressure is defined as the force applied per unit area, $P=\frac{F}{A}$. Mass per unit volume is density, speed is about how fast an object moves, and direction of force is not pressure. So pressure measures the amount of force applied per unit area.

Answer:

b) Newton's Second Law

Question 4