# Forces and Their Applications

In this worksheet, students will look at different types of forces and how they are used in everyday life.

Key stage:  KS 4

Curriculum topic:  Physics: Forces

Curriculum subtopic:  Calculating Work Done as Force x Distance

Difficulty level:

### QUESTION 1 of 10

The accelerator pedal in a car affects the pull of the engine, which provides a forward force. The effect of a force on an object depends on its mass. The same force would cause more acceleration to an object of a small mass than that of a bigger mass. This is the same for all object, they need a force to be able to accelerate them

If the forces acting on an object are balanced, it will either be at rest or moving at a constant speed. If the forces are unbalanced, the object will slow down or speed up and even start moving (if it was at rest previously). The result of unbalanced forces is called a net force.

Three variables affect the motion of an object: an unbalanced force (F), the object's mass (m) and the acceleration (a). F is proportional to m if a is constant, and the formula is:

F = m x a

The unit of force is Newton (N), where m is in kg and a is in m/s2. When thinking about motion, always bear in mind that there is some kind of friction or resistance force that is opposite to the direction of the movement.

A car driver cannot stop a car immediately. It takes him or her time to react; this time is called thinking time. Thinking time is longer, the higher the speed of the car. Thinking distance is the distance travelled between the moment a driver sees a danger ahead, and taking action to avoid it. Braking distance is the distance travelled before the car stops after the brakes have been applied. Braking distance increases as the speed of the car increases.

How can we increase the pull of the engine that provides the forward force?

By letting the accelerator pedal off.

By pressing the accelerator pedal down.

By pressing the brakes.

If the same force was applied to a number of objects with different masses, which object would accelerate more quickly?

Small

Medium

Large

What is the result of balanced forces on an object? Two options apply.

Deceleration

Constant speed

At rest

Acceleration

What would happen if unbalanced forces act on an object? Three options apply.

Motion

Slow down

Constant speed

At rest

Speed up

What do we call the force that is the result of unbalanced forces?

Top

Net

Total

Unbalanced

Is the following statement true or false?

The force acting on an object is proportional to its mass.

True

False

What is thinking time?

The time it takes for a driver to think whether he/she should stop when seeing danger.

The time it takes the car to stop from the moment the driver brakes.

The time it takes a driver to react from the moment they see danger.

What is thinking distance?

Thinking distance is the distance travelled between a driver seeing a danger and taking action to avoid it.

Thinking distance is the distance travelled between a driver seeing a danger and U-turning.

Thinking distance is the time it takes between a driver seeing a danger and braking.

What happens to the braking distance as the speed of the car increase?

Increases

Stays the same

Decreases

Calculate the force if an object has a mass of 70kg and an acceleration of 10m/s2.

200 N

70 N

700 N

• Question 1

How can we increase the pull of the engine that provides the forward force?

By pressing the accelerator pedal down.
EDDIE SAYS
We can increase the pull of the engine that provides the forward force by pressing the accelerator pedal down.
• Question 2

If the same force was applied to a number of objects with different masses, which object would accelerate more quickly?

Small
EDDIE SAYS
The same force would cause more acceleration to an object of a small mass than that of a bigger mass. F=ma, if m is small then a will be large.
• Question 3

What is the result of balanced forces on an object? Two options apply.

Constant speed
At rest
EDDIE SAYS
The result of balanced forces on an object are constant speed or the object will stay at rest. It is only able to accelerate when it has an unbalanced force acting on it.
• Question 4

What would happen if unbalanced forces act on an object? Three options apply.

Motion
Slow down
Speed up
EDDIE SAYS
If the forces are unbalanced, the object will slow down or speed up and even start moving (if it was at rest previously). If the forces become balanced at that point, then it will stay at the same speed.
• Question 5

What do we call the force that is the result of unbalanced forces?

Net
EDDIE SAYS
The force that is the result of unbalanced forces is called net force.
• Question 6

Is the following statement true or false?

The force acting on an object is proportional to its mass.

True
EDDIE SAYS
The statement is true - the force acting on an object is proportional to its mass. The equation shows us this because F=ma.
• Question 7

What is thinking time?

The time it takes a driver to react from the moment they see danger.
EDDIE SAYS
A car driver cannot stop a car immediately. It takes him or her time to react after seeing danger ahead; this time is called thinking time. Thinking time is longer, the higher the speed of the car.
• Question 8

What is thinking distance?

Thinking distance is the distance travelled between a driver seeing a danger and taking action to avoid it.
EDDIE SAYS
Thinking distance is the distance travelled between a driver seeing a danger and taking action to avoid it.
• Question 9

What happens to the braking distance as the speed of the car increase?

Increases
EDDIE SAYS
The braking distance increases as the speed of the car increases. There is more force needed to stop the car, and so it takes longer to be able to do that.
• Question 10

Calculate the force if an object has a mass of 70kg and an acceleration of 10m/s2.

700 N
EDDIE SAYS
force = mass x acceleration = 70 x 10 = 700 N
---- OR ----

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