This KS3 Science quiz asks questions on forces. It doesn't matter if something is moving or stationary, there are always forces acting on it. The famous Scientist, Isaac Newton, realised this and came up with his three laws of motion. Forces are measured in **newtons** which have the symbol **N**. One of the most famous of Newton's laws is that if an object isn't moving, the forces acting on it are equal and opposite.

Imagine a book lying down on a shelf. The book puts a downward force on the shelf. The shelf must therefore be putting exactly the same force back on the book. Now if you add a whole lot more books to the shelf, if the shelf can't push back with the same force that the pile of books is putting on the shelf, it moves - in other words, it collapses! The force a book puts on a shelf is its **weight**. Weight is therefore measured in newtons. Unfortunately, in everyday life, you will hear most people referring to weight using kilograms. This is entirely incorrect, kilograms are a measure of **mass**. Weight is the force created by the attraction of gravity on the mass of an object. On Earth, a mass of 100g (0.1kg) has a weight of about 1N.

1.

Which of the following statements about unbalanced forces is NOT true?

They can change the direction of a moving object

They can slow down an object

They have no effect on an object

They speed up an object

Unbalanced forces will ALWAYS create movement

2.

On Earth, 1kg weighs approximately 10N. What would be the weight of 500g?

1N

5N

50N

500N

500g = 0.5kg, 0.5kg weighs 0.5 x 10 = 5N

3.

Friction .......

doesn't affect a moving object

slows a moving object

speeds up a moving object

starts an object moving

Friction is a force

4.

Which of the following statements about balanced forces is NOT true?

A moving object will continue to move at constant speed

A stationary object will not move

They are the same size acting in the opposite direction

They are the same size acting in the same direction

This is Newton's third law of motion

5.

A spring can be stretched by hanging masses on it. Which of the following is true?

The larger the force, the greater the stretch

The smaller the force, the greater the stretch

The spring does not exert a force on the mass

The mass does not exert a force on the spring

According to Newton's third law of motion, if the mass puts a force on the spring, the spring must be putting a force on the mass

6.

What is force measured in?

Joules

Kilograms

Newtons

Pascals

Forces can act in any direction. When drawing forces, you must always show in which direction they are acting

7.

On Jupiter, 1kg weighs approximately 25 newtons. What would be the weight of 100g?

0.25N

2.5N

250N

2500N

100g = 0.1kg, 0.1kg weighs 0.1 x 25 = 2.5N. The weight of an object depends on the force of gravity that is acting on it. The Moon has a gravity of about one sixth of that of the Earth, so 1kg would weigh a lot less than on the Earth, whilst on the planet Jupiter, it would weigh a lot more as the force of gravity there is larger

8.

What is weight measured in?

Joules

Kilograms

Newtons

Pascals

Weight is a force and therefore should be measured in newtons

9.

Which of the following is NOT a force?

Gravity

Mass

Pull

Weight

Mass is measured in grams, kilograms etc

10.

Which of the following is NOT a touching force?

A push

Air resistance

Friction

Magnetism

Magnets attract or repel at a distance, they do not need to touch the object they are acting on to have an effect