# Investigate 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

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 objects -  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, or even start moving (if it were 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 the 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.

Lots of important stuff to get your head around here. Let's get on to the questions and see how much you can remember!

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 were 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?

Deceleration

Constant speed

Remains at rest

Acceleration

What would happen if unbalanced forces act on an object?

Motion

Slow down

Constant speed

Remain 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 doing a U turn

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 a car increases?

Increases

Stays the same

Decreases

Calculate the force if an object has a mass of 70 kg and an acceleration of 10 m/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
How did you find this first question? Imagine yourself driving a car and wanting to give more force to the engine. How do you think you could do this? We could increase the pull of the engine providing the forward force by pressing the accelerator pedal down. The harder you press on the pedal, the greater the force you will be giving to the engine.
• Question 2

If the same force were 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 = m x a so if m (mass) is small then a (acceleration) will be large. Does that make sense?
• Question 3

What is the result of balanced forces on an object?

Constant speed
Remains at rest
EDDIE SAYS
If you think about what the word 'balance' actually means, this question will become easier. If something is balanced then it will stay exactly as it is. The result of balanced forces on an object will be either a 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?

Motion
Slow down
Speed up
EDDIE SAYS
There were three correct options this time. Did you get them all? If forces are unbalanced, an object will either slow down or speed up, or even start moving (if it were at rest previously). If the forces become balanced at that point, then it will remain at the same speed.
• Question 5

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

Net
EDDIE SAYS
Oh this is a bit harder! Did you know the word 'net' in this context? It is used when you need to compare differing amounts of something such as your 'net' salary, which is the amount you earn after deducting the tax you have to pay. Net movement is the final or total amount of movement once you have taken into account the forces acting in both directions. So, 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
Another tricky question but just remember that useful equation and you'll see that all those factors of acceleration, force and mass are closely related. The statement is true - the force acting on an object is proportional to its mass. The equation shows us this because F = m x a.
• Question 7

What is thinking time?

The time it takes a driver to react from the moment they see danger
EDDIE SAYS
Did you get caught out by the first option here? It was almost correct but once you read on to the third option, you can see that it is the last one that is the correct answer. 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.
• 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. Thinking distance increases the faster the car is travelling.
• Question 9

What happens to the braking distance as the speed of a car increases?

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. This is something that drivers need to be aware of, especially when they are driving in poor visibility such as rain or fog. It will take longer to stop the car the faster speed they are driving at. When you learn to drive, you will be expected to know about braking distances. At last, you can see a reason why you learn all of this stuff!!
• Question 10

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

700 N
EDDIE SAYS
Right then, here's a lovely maths sum to do - you've just got to remember the all-important equation: force = mass x acceleration. We know that the mass is 70 kg and the acceleration is 10 m/s² So, the force = 70 x 10 = 700 N How did you do with that calculation? Just learn the equation and you'll find these questions a doddle! Another activity completed - you're flying through all this physics. Well done!
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