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Balanced and Unbalanced Forces

This worksheet explores the question 'how do forces affect speed?'

'Balanced and Unbalanced Forces' worksheet

Key stage:  KS 3

Curriculum topic:  Physics: Motion and Forces

Curriculum subtopic:  Motion and Forces

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

For an object to move the forces on it must be unbalanced.

In the diagram below the duck, is floating on the water. It is not moving up or down because the force acting downwards caused by gravity is equal to the force of the water pushing up onto the duck (upthrust).

 

 

The force of gravity (red arrow) is equal to the upthrust (green arrow) from the water.

 

The car shown below is accelerating because the driving force (green arrow) is greater than the drag caused by air resistance (red arrow).

 

 

The car is accelerating left to right becasue the driver force is greater than the air resistance

 

When the drag is greater than the driving force the car will slow down, but if they are balanced and the car is already moving, it will continue to move at a constant speed. This is described in more detail in Isaac Newton's 'Laws of Motion'.

 

There are many forces acting on a skydiver when he leaves the plane:

 

 

As a skydiver leaves the plane he accelerates downwards due to gravity, but as his speed increases, so does the air resistance. This continues until both forces are balanced and the skydiver will fall at a constant speed, called terminal velocity. 

Complete the sentence below by typing the missing word into the text box.

 

When an object is stationary then the forces on it are _____________.

Complete the sentence below by typing the missing word into the text box:

 

When an object is moving then the forces on it are _____________.

Complete the following sentence by selecting one of the options below:

 

If a ball falls a short distance, the downwards force is........

smaller than the air resistance

greater than the air resistance

equal to the air resistance

Complete the following sentence by selecting one of the options below:

 

At terminal velocity the downwards force is.....

smaller than the air resistance

greater than the air resistance

equal to the air resistance

Complete the following sentence by selecting one of the options below:

 

A cyclist peddles to 10 m/s and then stops peddling, which results in his speed decreasing because the driving force is....

smaller than the air resistance

greater than the air resistance

equal to the air resistance

A harrier Jump-jet is capable of hovering as well as performing many manoeuvers which require forces in all directions. 

 

 

Complete the table below to give the direction of the force when the plane is moving 

 forces balanced downwards force high upthrust high
moving downwards
moving upwards
hovering

Complete the table below showing the forces on a skydiver at various points during the jump.

 

 forces balanced downwards force high upthrust high
accelerating downwards
terminal velocity
parachute deployed

Complete the table below showing the forces on a car when moving. 

 

 forces balanced drag high drive high
accelerating
steady speed
decelerating
  • Question 1

Complete the sentence below by typing the missing word into the text box.

 

When an object is stationary then the forces on it are _____________.

CORRECT ANSWER
balanced
EDDIE SAYS
When an object is stationary, the forces acting upon it are balanced.
  • Question 2

Complete the sentence below by typing the missing word into the text box:

 

When an object is moving then the forces on it are _____________.

CORRECT ANSWER
unbalanced
EDDIE SAYS
When an object is moving then the forces are unbalanced.
  • Question 3

Complete the following sentence by selecting one of the options below:

 

If a ball falls a short distance, the downwards force is........

CORRECT ANSWER
greater than the air resistance
EDDIE SAYS
The forces will be unbalanced, with the downward force being greater than the air resistance . This means that the ball will fall downwards. The forces will only be equal at terminal velocity and that wont occur over a short distance.
  • Question 4

Complete the following sentence by selecting one of the options below:

 

At terminal velocity the downwards force is.....

CORRECT ANSWER
equal to the air resistance
EDDIE SAYS
At terminal velocity the forces are balanced so the object will continue to move at a constant speed.
  • Question 5

Complete the following sentence by selecting one of the options below:

 

A cyclist peddles to 10 m/s and then stops peddling, which results in his speed decreasing because the driving force is....

CORRECT ANSWER
smaller than the air resistance
EDDIE SAYS
Air resistance or drag along with friction slows the cyclist down.
  • Question 6

A harrier Jump-jet is capable of hovering as well as performing many manoeuvers which require forces in all directions. 

 

 

Complete the table below to give the direction of the force when the plane is moving 

CORRECT ANSWER
 forces balanced downwards force high upthrust high
moving downwards
moving upwards
hovering
EDDIE SAYS
Harrier Jump-jets hover, to allow them to land on aircraft carriers more easily.
  • Question 7

Complete the table below showing the forces on a skydiver at various points during the jump.

 

CORRECT ANSWER
 forces balanced downwards force high upthrust high
accelerating downwards
terminal velocity
parachute deployed
EDDIE SAYS
The parachute increases the air-resistance which slows the diver down.
  • Question 8

Complete the table below showing the forces on a car when moving. 

 

CORRECT ANSWER
 forces balanced drag high drive high
accelerating
steady speed
decelerating
EDDIE SAYS
The drag slows the car down but breaks increase the rate of deceleration.
---- OR ----

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