Year 7 & 8 TOC

Force

The force

LO: Investigating the effects of applying different forces to familiar object
What is a force and how to measure it

Force is just a fancy word for something that pushes and pulls. It’s the push or pull that happens when 2 objects interact. If we push a chair, we are applying a force to it. If I pick up a coffee cup, I am apply a force to it. If I jump I am applying force.

Did you know? An apple a day for gravity

Forces in life

Forces act on everything around us. There’s usually more than one force acting on any object at one time but you probably don’t even notice it. Gravity pulls objects towards each other, like a person towards the ground. Its the force which keeps us revolving around the sun, and brings us down to the ground when we jump.

When you kick a ball, you use energy to create a push force. This force causes the ball to move. If you’re a goal keeper and you catch the ball, you’re still exerting a push force but you’re causing the ball to stop.

Types of Forces

There are some forces we can see in action and others we can’t, but we know that forces are always acting on us. Forces can be contact or non-contact.

Contact Forces

When forces act, due to touching they are called a contact force. Friction, tension force, spring force, applied force and normal force. Some forces make objects move because of a direct push or pull, like throwing a ball. Let’s talk about friction a little bit later.

Non-Contact Forces

Non-contact force don’t need to touch the object to have an effect on them (gravity and magnetic forces). If you place 2 magnets next to each other, you’ll see that they attract or repel each other without touching. This is an example of magnetic force, a non-content force. We’ll talk more about non-contact forces later in this chapter.

Measuring forces

We can measure forces in a variety of ways. When you step on a scale, your measuring the Earth’s gravitational pull on you.

If we want to get more scientific we can use a spring balance. A spring balance is a stiff spring, which stretches as an object pulls on it. As the spring stretches the marker moves, allowing you to measure the amount of force. You can measure force without a spring balance, by using a ruler and rubber band.

We don’t measure forces in kg or Pounds. We measure forces in Newtons (N).

The reason we use Newtons, is for simplicity. Scientists around the world can communicate and share information, with out having to convert information. 100 grams is equal to 1 newton. This means if you hold a 5kg (5000g) dumbbell in your hand, your lifting 50 newtons.