AnswersPOP Physics 2627Lesson 2: Newton's First and Third Laws

Newton's Second Law Answers

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Devon has several toy car bodies and motors. The motors have the same mass, but they provide different amounts of force, as shown in this table.The bodies have the masses shown in this table.

Question illustration
A
motor 1, with body 1
B
motor 1, with body 2
C
motor 2, with body 1
D
motor 2, with body 2
2
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How much force is needed to accelerate an object of mass 90 kg at a rate of 1.2 m/s2?

A
0.013 N
B
75 N
C
108 N
D
1080 N
3

A baseball has a mass of 145 g. A bat exerts a force of 18,400 N on the ball. What is the acceleration of the ball?

A
1.27 x 102 m/s2
B
2.67 x 103 m/s2
C
1.27 x 105 m/s2
D
2.67 x 106 m/s2
4

Newton’s second law of motion states that the acceleration of an object is proportional to the net force acting on it.

Answer not available
5

Juanita studies several free-body diagrams in which a normal force is shown. What is always true about a normal force in a free-body diagram?

A
It is opposite the weight.
B
It is perpendicular to a surface.
C
It is opposite the net force.
D
It is parallel to a surface.
6

The gravitational acceleration on Earth is 9.8 m/s2. What is the weight of a car on Earth (to the nearest whole number) if it has a mass of 1360 kg?

A
14 N
B
139 N
C
1333 N
D
13,328 N
7

An object pulled to the right by two forces has an acceleration of 2.5 m/s2. The free-body diagram shows the forces acting on the object.

Question illustration
A
50 N
B
98 N
C
313 N
D
490 N
8

What is the mass of an object if a net force of 8.0 N causes it to accelerate at 1.1 m/s2?

A
6.9 kg
B
7.3 kg
C
8.8 kg
D
9.1 kg
9

Chang sees the following formula on a website about Newton’s second law. a =

Question illustration
A
He needs to find the net force acting on the object in a direction.
B
He needs to use only forces acting in the direction of motion.
C
He needs to combine the horizontal and vertical forces.
D
He needs to multiply the horizontal and vertical forces.
10

The gravitational acceleration on the moon is about one-sixth the size of the gravitational acceleration on Earth. According to Newton’s second law of motion, what happens to an astronaut who goes to the moon?

A
The astronaut’s weight decreases because the moon’s gravitational acceleration is greater than Earth’s.
B
The astronaut’s weight increases because the moon’s gravitational acceleration is greater than Earth’s.
C
The astronaut’s weight decreases because the moon’s gravitational acceleration is less than Earth’s.
D
The astronaut’s weight increases because the moon’s gravitational acceleration is less than Earth’s.
11

A rocket experiences a constant force even as the amount of fuel in its fuel tanks decreases. What happens to the acceleration of the rocket as it runs out of fuel?

A
The acceleration decreases because the mass increases.
B
The acceleration increases because the mass increases.
C
The acceleration decreases because the mass decreases.
D
The acceleration increases because the mass decreases.
12

A box that has a mass of 80 kg slides down a ramp with a 30 degree angle. The free-body diagram shows the forces acting on the box.

Question illustration
A
0.5 m/s2
B
4.9 m/s2
C
8.5 m/s2
D
9.8 m/s2
13

Which formula is used to calculate the mass of an object if the force and acceleration are known?

A
m = Fa
B
m =
Option B
C
m =
Option C
D
m = F – a

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