Forces in two dimensions (including resolution of a force) | Combined science

Starter quiz

How many newtons (N) are there in 53 kN?

5300 N

53 000 N ✓

530 000 N

53 000 000 N
The diagram shows a force arrow drawn on a grid of 1 cm squares. What is the magnitude of the force?

left

right

3 N

6 N

12 N ✓
There is a law of physics which states that an object will remain at rest, or in motion in a straight line at constant speed, unless a resultant force is acting on it. What is the name of this law?

Newton’s First Law of motion ✓

Newton’s Second Law of motion

Newton’s Third Law of motion

Newton’s Fourth Law of motion
What is the magnitude of the resultant force in this diagram?

203 N ✓

248 N

253 N

293 N
The diagram shows an object with a single force acting on it. Which of the following are possible descriptions of the object’s motion?

The object is moving to the left at constant speed.

The object is moving to the right at constant speed.

The object is accelerating. ✓

The object is decelerating. ✓
A child throws a ball straight up. Which of the following is a correct free body diagram of the ball as it travels upwards?

Exit quiz

A helicopter is in the air in a state of equilibrium. Which of the following motions are possible?

It is moving upwards at constant speed. ✓

It is falling with decreasing speed.

It is travelling in a circle.

It is stationary. ✓
A duck is swimming in a straight line across the surface of a lake at a steady speed. Which of the following free body diagrams correctly shows the forces acting on the duck?
An aeroplane and its free body diagram are shown. Which of the following are possible descriptions of the aeroplane’s motion?

Moving to the left at decreasing speed. ✓

Moving downwards at increasing speed.

Moving up at increasing speed, while also moving steadily to the right.

Moving to the left at decreasing speed, while also moving steadily upwards. ✓

Moving to the left at decreasing speed, while also moving steadily downwards. ✓
A spaceship in space uses two rockets to produce forces acting in two directions at the same time. Which of the following vector diagram shows how to find the resultant force?
The vector diagram shows the addition of three forces to find the resultant force. What is the magnitude of the resultant force?

40 N ✓

60 N

63 N

72 N
The vector diagram shows a force on a grid of 1 cm squares. Which of the following is the correct description of the horizontal component of the force?

30 N upwards

30 N downwards

40 N to the right

40 N to the left ✓

50 N upwards and to the left

Worksheet

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Lesson Details

Key learning points

A free body diagram shows all of the forces acting on a single object
The resultant of two forces can be determined by adding individual forces on a vector diagram
The resultant of two perpendicular forces is in a different direction from either of these forces
A single force can be resolved into two components acting at right angles to each other
The two component forces together have the same effect as the single force

Common misconception

The velocity of an object must be in the same direction as the resultant force acting on the object.

Invite pupils to consider situations in which the resultant force is not in the same direction as the velocity, such as an object that has been thrown upwards and is slowing down as its height increases.

Keywords

Resultant force - is a single force that represents the effect of all the forces on an object.
Equilibrium - is the state of an object if there is no resultant force acting on it.
Vector diagram - is a drawing on which forces are drawn end to end and to scale, which can be used to find a resultant force.
Component of a force - is one of two perpendicular forces that add up to a single force.
Resolving forces - splits a force into two perpendicular forces that add up to that force.