Questions on Moments
Q3. The drawing shows a very old set of scales. It can be used to check the weights of silver coins.
(a) Jack puts a silver coin in pan X. There is nothing in pan Y.
In which direction does pan X move?
Down 
anticlockwise
(1 mark)
(b) The table shows the weights of five silver coins.
Silver Coin |
A |
B |
C |
D |
E |
weight in mN |
112 |
106 |
120 |
112 |
98 |
Jack puts one coin in each pan of the scales.
Which two coins will make the scales balance?
(Give the letters).
A and D
(1 mark)
(c) Coin A is placed in pan X, and coin C is placed in pan Y.
In which direction does pan X now move?
up
accept clockwise
(1 mark)
(d) In another experiment, coin B is placed in pan X, and one of the other coins is placed in pan Y.
Pan X goes down. Which coin is in pan Y?
Give the letter.
E
(1 mark)
(e) Jack knows the weights of the five silver coins in the table. He also has a gold coin.
Explain how he could use the silver coins and the scales to find the approximate weight of the gold coin.
Put the gold coin in one pan and put the coins on in turn to find out which are lighter/heavier. If all are lighter he should then start to put on combinations of coins until he has a lowest value that is heavier and highest one that is lighter. He then knows the coin's weight is somewhere between the two values.
(2 marks)
Total 6 marks
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