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Questions on Moments

Q1. A mother makes a simple mobile for her young daughter. She uses plastic animals as shown below.

(a)

(i) The elephant weighs 0.6 N.

What is the turning moment produced by the elephant about point X?

Moment = Fd = 0.6 N x 8 cm = 4.8 N cm

(2 marks)

(ii) The mobile balances.

What is the turning moment produced by the monkey about point X?

It balances - so it is the same as that for the elephant = 4.8 N cm

A mark was given for the same answer to part (i)

(1 mark)

(iii) What is the weight of the monkey?

0.3 N

because 0.3 N x 16 cm = 4.8 N cm

(1 mark)

(b) What is the size of the tension (force) in string A?

The force in the string is equal to the sum of the forces pushing down = 0.3N + 0.6 N = 0.9 N

The mark was given for the answer to part a (iii) plus 0.6 N

(2 marks)

Total 6 marks