Gr 9 – Pressure worksheet
1 Explain why a 4x4 driving in soft sand, will perform better by not getting stuck if its
tyres are deflated.
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2 A rectangular block of mass 25 kg measures 10 cm by 40 cm by 1,2 m.
i. Calculate the weight of the block.
ii. Draw a diagram to show how the block must rest to exert the
maximum pressure on the ground.
iii. Using what you have calculated in 6.2.1 and 6.2.2, calculate the
maximum pressure (in Pa) that the block can exert.
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3 A hydraulic lift is shown below. Piston A has a contact area of 3,3 cm2 and B, one of
0,66 m2. A force of 20 N acts on piston A.
?
B
20 N
A
i. Convert the area of piston A into m2.
ii. Calculate the weight that can be lifted by piston B.
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4 The density of the water in the school’s waterpolo pool is 1000 kg/m3 and its depth is
2,5 m. Calculate
i. the pressure (in kPa) due to the water at the bottom of the pool.
ii. the total pressure at the bottom of the pool.
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5 Using pressure concepts, explain why a drawing pin is designed the way it is.
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6 A rectangular block of mass 45 kg measures 60 cm by 40 cm by 1,3 m.
i. Calculate the weight of the block.
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ii. Draw a diagram to show how the block must rest on one of its faces, to
exert the minimum pressure on the ground.
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iii. Using what you have calculated in 6.2.1 and drawn in 6.2.2, calculate
the minimum pressure (in Pa) that the block can exert.
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7 Below is a simple type of braking system. The areas of the cross-section of the small
and large cylinders are 0,0004 m2 and 0,0024 m2 respectively. The brake pedal is
pushed so that the force on the small cylinder is 90 N.
i. Determine the pressure exerted on the brake fluid.
ii. Determine the force exerted by the large piston on the brakes.
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8 A J-tube has some mercury poured
into it as shown. Calculate the
pressure
15 cm
A
i. exerted on the gas at A by the mercury alone.
ii. exerted on the gas at A by both the mercury and atmosphere.
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