2.2 - Newton's Laws

Question 1

What is mass? What is it measured in?

Answer 1

The amount of matter in an a object (kg)

Question 2

What is weight? What is it measured in?

Answer 2

The force that acts on an object due to gravity and the objects mass (N)

Question 3

What is a force?

Answer 3

A push or pull acting on an object due to an interaction with another object

Question 4

Find the weight of a person on Earth if they have a mass of 65 kg (g = 10 N/kg)

Answer 4

W = m × g

= 65 kg × 10 N/kg

= 650 N

Question 5

What is the gravitational field strength on the moon?

Answer 5

1.6 N/kg

Question 6

What is the mass of a person who weighs 120 N on the Moon? (g = 1.6 N/kg)

Answer 6

m = W ÷ g

= 120 N ÷ 1.6 N/kg

= 75 kg

Question 7

What is inertia?

Answer 7

A resistance to a change in motion

Question 8

What is inertial mass?

Answer 8

A measure of how difficult it is to change a given object’s velocity

Question 9

What is Newton’s first law?

Answer 9

A body will remain in a state of rest or in uniform motion in a straight line unless acted upon by an external resultant force

Question 10

State the defining equation for Newton’s Second Law. Give appropriate units.

Answer 10

Resultant force (N) = Mass (kg) = Acceleration (m/s^2)

Question 11

Acceleration and mass are ______ proportional. This means that if the mass of the vehicle doubles, the acceleration halves if the resultant force doesn’t change.

Answer 11

inversely

Question 12

What will unbalanced forces cause?

Answer 12

acceleration
deceleration
change in direction

Question 13

If an object changes direction but remains at a constant speed, is there a resultant force?

Answer 13

Yes , since there is a change in direction, there is a change in velocity and so there must be a resultant force.

Question 14

What is resultant force

Answer 14

The leftover or net force when all the forces acting on the object have been combined.

Question 15

What happens if there is zero resultant force?

Answer 15

The object will remain stationary or continue to move with a constant speed and direction.

Question 16

A car weighs 1,000 kg. The resultant force is 5,000 N. What is its acceleration?

Answer 16

Acceleration = resultant force ÷ mass

a = 5,000 N ÷ 1,000 kg = 5 m/s

Question 17

Resultant force and acceleration are _____ proportional. If the resultant force doubles, the acceleration of the vehicle also doubles if the mass of the vehicle is the same.

Answer 17

directly

Question 18

What is the gravitational field strength on the surface of Earth?

Answer 18

10 N/kg

Question 19

What is the approximate weight of a 1kg object on the surface of Earth?

Answer 19

10 Newtons

Question 20

When does a falling object reach terminal velocity?

Answer 20

When the upwards forces (air resistance) and the downwards forces (weight) are equal to each other.
No resultant force, so constant speed.

Question 21

What happens to the magnitude of air resistance on a falling object when the velocity increases?

Answer 21

As velocity increases, the force of air resistance on the object will also increase.

Question 22

Moving through the air causes collisions with air molecules. There is friction between the moving body and the particles, which causes some of the ____ energy of the moving body to be converted into heat. Additionally, the air molecules bounce off the object gaining ___ energy.

The faster an object moves, the greater the number of collisions with air molecules. This increases ____, and the air molecules bouncing off gain even more ____ energy

Answer 22

Kinetic

friction

Question 23

Opening the parachute provides a large surface area. This produces a huge drag force in the opposite direction to movement, slowing the skydiver down. When the parachute opens, forces become unbalanced (drag is greater than weight), and this gives a big resultant force in the opposite direction to movement, causing ______

Answer 23

deceleration

Question 24

What is Newton’s Third Law?

Answer 24

Whenever two objects interact, the forces they exert on each other are equal and opposite.

Question 25

Simplify Newtons 3rd Law and give an example involving a car crash.

Answer 25

If body A exerts a force on body B, B exerts an equal and opposite force on A. For example, if car A crashes into car B with a force of 10,000 N, then car B exerts a force of –10,000 N back on car A.