The base of the table has an area of 1600 cm2. Some books are also placed on the table. The books, glass of water and table exert a pressure of 0·1 N/cm2 on the ground.
Calculate the force exerted on the ground by the books, glass of water and table. Assume that the whole of the base of the table is in contact with the ground. [2]
(c) In fact, the assumption made in part (b) is incorrect. Part of the base of the table is not in contact with the ground.
Describe how this changes your answer to part (b). [1]
Mark scheme (a)
Scheme
Marks
Comments
\(9.6 \div 12\ (= 0.8)\)
M1
\(0.8 \div 8 \times 3\)
M1
FT ‘their 0.8’ including place value error from conversion of kg to g
0.3 (kg) or 300g
A1
CAO
Alternative method
Scheme
Marks
Comments
88 : 3 : 5
B1
\(\dfrac{3}{88+3+5} \times 9.6\)
M1
0.3 (kg) or 300g
A1
CAO
Mark scheme (b)
Scheme
Marks
Comments
(Total force =) \(1600 \times 0.1\)
M1
160 (N)
A1
Mark scheme (c)
Scheme
Marks
Comments
Valid impact e.g. ‘The force would be less’
E1
Ignore any extraneous comments e.g. ‘The pressure would increase, and the force will be lower’.
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