The spring balance

The idea

A spring balance has a spring fixed at one end and a hook at the other; an object hung on the hook stretches the spring, and the stretch, read on a scale in newton, gives its weight.

Reading a weight

A spring balance has a spring and a hook.

How do you think it shows the weight of an object?

• By how much the spring stretches
• By the colour of the spring
• By the length of the table

Use the balance

Hang each bag on the hook. Watch the spring and the pointer.

The stretch is the weight

The heavier bag stretched the spring more. The pointer moved along a scale marked in newton, so the scale gives the weight.

A spring balance has a spring fixed at one end and a hook at the other. An object hung on the hook stretches the spring. The stretch, read on a scale in newton, gives the weight.

Notes

A spring balance has a spring and a hook. The stretch of the spring, read on a scale in newton, gives the weight.

Check yourself

What stretches the spring of a spring balance?

The weight is read from …

A heavier object is hung on the hook. The spring …

A spring balance measures …

• The colour of the object. Colour does not stretch the spring. The weight does.
• The weight of the object hung on the hook — correct. Yes!
• The size of the room. The room has no part in it. The weight of the object stretches the spring.
• the colour of the hook. The scale shows the weight.
• the shape of the object. The stretch of the spring, read on the scale, gives the weight.
• the scale marked in newton — correct. Yes!
• stretches more — correct. Yes!
• stretches less. A heavier object has more weight and stretches the spring more.
• does not change. The stretch depends on the weight.
• colour. A spring balance shows the weight, a force.
• weight — correct. Yes!
• temperature. A spring balance shows the weight, a force.