# Force and Velocity

In this worksheet, students will look at speed and the effects that forces have on speed.

Key stage:  KS 3

Curriculum topic:   Physics: Motion and Forces

Curriculum subtopic:   Motion and Forces

Difficulty level:

### QUESTION 1 of 10

Velocity is a term used to describe the speed of an object in a particular direction. For example the two cyclists below are travelling at the same speed but different velocities.

Cyclists travelling at 5 m/s but in different directions

Applying a force to an object affects the velocity of the object. Forces can change the velocity of an object in several ways by:

• making the object go faster or slower
• stopping a moving object
• changing the direction of a moving object
• making a stationary object move.

When the velocity of an object, such as a car, increases, then the car is said to be accelerating.

When an object is slowing down, then it is decelerating. The ball shown below is decelerating because the force of the net against it is slowing it down.

Sir Isaac Newton stated in his Laws of Motion that, if there are no forces acting on an object, then:

• If the object is at rest, it will remain at rest.
• If the object is moving, it will continue to move at a steady speed in a straight line.

These laws can be tested in space, because there is no air in space to affect the movement of the objects.

Imagine that you accelerate to 200 miles per hour in a space ship in space, then you turn off the engines. The space ship will continue to travel at 200 miles per hour forever because there are no forces, such as air resistance acting on the space ship.

On Earth, there are forces such as air resistance and friction that slow moving objects down.

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

Velocity is the speed of an object in a particular __________ .

Which famous scientist developed the Laws of Motion?

Isaac Newton

Albert Einstein

Brian Cox

Charles Darwin

When a object increases its speed, it is said to be...........

decelerating

accelerating

accentuating

fermenting

When a car travels along the motorway at 70 miles per hour and the driver takes his foot off the accelerator pedal, what two forces are responsible for slowing the car down?

friction

air resistance

pressure

Complete the sentence by selecting the missing words from the options below.

When there are no forces acting on an object, if stationary, it will _________  ___________.

start moving

remain stationary

slow down

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

When there are no forces acting on an object, if moving, it will continue to move at a steady speed in a  ___________ line.

Forces can change the velocity of an object.

Which ONE of the following will not be affected by applying a force to the object?

direction

speed

colour

movement

What force is reduced when an ice skater takes to the ice, which allows them to travel quickly and with less effort?

air resistance

friction

gravity

pressure

• Question 1

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

Velocity is the speed of an object in a particular __________ .

direction
EDDIE SAYS
Velocity is the speed of an object in a particular direction; for example, "the ball fell towards the Earth (direction) with a speed of 5 m/s (speed)".
• Question 2

Which famous scientist developed the Laws of Motion?

Isaac Newton
EDDIE SAYS
Sir Isaac Newton was a brilliant scientist and the units that we use to measure force were named after him.
• Question 3

When a object increases its speed, it is said to be...........

accelerating
EDDIE SAYS
When an object accelerates the speed of the object increases. That means that the force that drives it forward is increasing (the muscles in a cheetah's legs working harder, your arm hitting a tennis ball hard, etc.).
• Question 4

When a car travels along the motorway at 70 miles per hour and the driver takes his foot off the accelerator pedal, what two forces are responsible for slowing the car down?

friction
air resistance
EDDIE SAYS
Friction is caused by the tyres' contact with the road surface, combined with the air resistance pushing against the car slow it down.
• Question 5

Complete the sentence by selecting the missing words from the options below.

When there are no forces acting on an object, if stationary, it will _________  ___________.

remain stationary
EDDIE SAYS
When no force is applied to a stationary object, it will remain stationary. That makes sense, doesn't it? No forces causing movement = no movement.
• Question 6

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

When there are no forces acting on an object, if moving, it will continue to move at a steady speed in a  ___________ line.

straight
EDDIE SAYS
When no force is applied to a moving object then it will continue to move at a steady speed in a straight line. It's basic stuff, isn't it? If you get forces, you'll know that in order for the moving object to change its speed or direction, there has to be a change in the forces acting upon it.
• Question 7

Forces can change the velocity of an object.

Which ONE of the following will not be affected by applying a force to the object?

colour
EDDIE SAYS
Applying a force to an object can have an impact on the speed and direction of an object, as you'll appreciate - so, that's its movement. The colour - clearly not. Mind you, if its movement took it into a tunnel lit by orange sodium lamps, then its colour would APPEAR to change, but that's another story!
• Question 8

What force is reduced when an ice skater takes to the ice, which allows them to travel quickly and with less effort?

friction
EDDIE SAYS
The smooth surface of the ice reduces the force of friction and allows the skater to move with ease across the ice.
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