Newton's first law

Question 1

What is Newton’s first law?

Answer 1

A body will remain at rest or continue in a straight line at a constant speed as long as the forces acting on it are balanced.

Question 2

If a body has a force of 10 N to the right, and 5 N to the left, which direction will it move in and with what force?

Answer 2

5 N to the right.

Question 3

A ball is stationary. The weight acting on it is 25 N. What is the size of the other force?

Answer 3

25 N

Question 4

Explain how the direction of a moving body can be made to change.

Answer 4

The forces acting on the moving body are in different/opposite directions of different sizes,
or a diagram drawn to show this.

These forces could be antiparallel or even at an angle, such as at 90° to the initial movement.

A change in direction will occur if the forces oppose the original motion or act in a way to change the direction.

Question 5

What effect will a 300 N forward force from the engine with a 200 N drag, have on a car?

Answer 5

Resultant force = 300 N - 200 N = 100 N
The car will accelerate in the direction of the resultant force.
Its velocity will increase.

Question 6

What effect will a 200 N forward force from the engine with a 400 N friction from brakes, have on a car?

Answer 6

Resultant forced = 200 N - 400 N = -200 N (200 N acting backwards).
The car will accelerate in the direction of the resultant force.
This is the opposite direction to the velocity, so the car will slow down.

Question 7

What will a resultant force acting in the opposite direction to the movement of a body do?

Answer 7

It will slow it down.

It can also reverse the direction of motion.

Question 8

What effect will a 300 N forward force from the engine with a 300 N drag, have on a car?

Answer 8

Resultant force = 0 N.

The car will continue to move at the same velocity.

Question 9

State what forces act on a body that is moving at a constant speed.

Answer 9

balanced or equal and opposite OR no forces acting

Question 10

Draw diagrams to show how two forces of 100 N acting on a mass can make it:

a) stationary
b) move at a constant speed
c) accelerate to the left

Answer 10

diagrams showing:

a) equal forces of 100 N and opposite OR no forces shown;
b) equal forces of 100 N and opposite forces shown;
c) two forces of 100 N both acting to the left.