1 the Diagram Shows a Bird Perched on a TV Aerial

HELP

1 The diagram shows a bird perched on a TV aerial.

a i What happens to the aerial when the bird lands on it?

ii What name is given to the effect of the bird's force on the aerial?

iii What force on the bird is causing this effect?

b i What will happen if the bird moves towards the centre of the aerial?

ii Why will this happen?

c i What will happen if another bird lands on the opposite side of the aerial?

ii Why will this happen?

CORE

2 Look at Sally and Sammy on a see-saw.

a i Sally and Sammy weigh the same. Where should they sit to make the see-saw balance?

ii Explain why this will make it balance.

b i Sammy's dog jumps onto her lap. What will happen to the see-saw?

ii Explain why this will happen.

iii What could Sammy do to make the see-saw balance again?

iv What could Sally do to make it balance?

3 Think about the picture of the crowbar.

a Where should John push on the crowbar to have the greatest effect?

b In which direction must he push?

c Explain why this will be the best way to use the crowbar.

d Describe where, on the crowbar, the pivot would be.

EXTENSION

4 The diagram shows a balance set that is often used in infant school maths. You may have used one yourself several years ago. It is used to teach children how numbers relate to each other. For example, if you put a single tag onto the number 6 peg on the left, you could balance it with two tags on the number 3 peg on the right. This shows that two lots of three equals six.

a Teresa is using a number balance to test out ideas about moments. Each number is 1 cm away from the ones next to it. Number 1 is 1 cm away from the pivot. All the tags weigh 5 N.

i With the balance set up exactly as shown in the picture, calculate the value for the anticlockwise moment, on the left-hand side. (Hint: Be careful about the unit you give for the moment!)

ii What would be the value of the moment of the clockwise force on the right-hand side to balance the set-up in a i ?

iii How many tags must Teresa hang on the number 8 mark on the right-hand side to balance the set-up in a i ?

b Teresa removes all the number tags. Then she hangs one tag on the number 10 mark, on the left-hand side.

i Calculate the anticlockwise moment produced by this tag.

ii Suggest one way in which Teresa could make the beam balance again, without changing the left-hand side.

c Teresa removes all the tags.

iWhat would happen to the beam if she now hangs two tags at the number 3 mark on the left-hand side and four tags at the number 2 mark on the right-hand side?

ii Explain your answer.

This worksheet may have been altered from the original on the CD-ROM.