Page 146 - Physics

Physics for Secondary Schools

Fins Buildings are constructed with wide
foundations as seen in Figure 7.9 to
ensure that the weight of a building acts
over a large area. As a result, the pressure
exerted by the building on the ground is
considerably reduced.

Figure 7.6: Fish fi ns

A sharp heel has a small area over which
the body’s weight (force) exerts pressure.
Also, it is notable that when one walks on
shoes with sharp-pointed heels, shown
in Figure 7.7 (a), the sharp-pointed heels
exert greater pressure on the ground than Foundation
the fl attened sole, shown in Figure 7.7 (b). Figure 7.9: Foundation of a building

It is painful to walk with bare feet on
a road that is covered by pebbles. The
weight of the body exerts considerable
pressure on the sharp-edged pebbles
(a) Shoe with (b) Shoe with whose surface area is small. The pebbles
pointed heel fl at sole exert an equal reaction on the feet.

Figure 7.7: Sharp-pointed heel and fl at sole Exercise 7.1
shoes
Answer all questions
During the construction of a railway line, (Use g = 10 N/kg)
wide wooden or concrete sleepers are 1. A rectangular plastic block weighing
placed below the railway tracks, as shown 1.5 kg rests on a horizontal fl oor. If it
in Figure 7.8. This provides a large surface measures 40 cm × 30 cm × 20 cm,
area over which the weight of the train acts. calculate the greatest and least
This is a safety measure for rail tracks. pressure that the block can exert on

the fl oor.
2. Calculate the pressure under the feet
of a student, given the foot area
is 8 cm and the student's mass is
2
43.8 kg.
3. The mass of a cuboid is 60 kg. If it

measures 50 cm × 30 cm × 20 cm,
what is the maximum pressure that
Figure 7.8: Railway
it can exert on the fl oor?

140
Student’s Book Form One

Physics Form 1 Final.indd 140 16/10/2024 20:57