An elephant weighing 40,000 N stands on one foot of area 1000 cm2 whereas
a girl weighing 400 N is standing on one ‘stiletto’ heel of area 1 cm2
(i) Which of the two, elephant or girl, exerts a larger force on the ground and by how much ?
(ii) What pressure is exerted on the ground by the elephant standing on one
foot ?
(iii What pressure is exerted on the ground by the girl standing on one heel ?
(iv) Which of the two exerts larger pressure on the ground : elephant or girl ?
Answers
Explanation:
Weight of elephant=40000N
Area of one foot = 1000 cm
2
=1000×10
−4
m
2
Weight of girl=400N
Area of heel of girl = 1 cm
2
=1×10
−4
m
2
(a) Elephant has a larger weight of 40000N, therefore, elephant exerts a larger force on the ground. Elephant exerts a larger force on the ground by 40000N - 400 N = 39600 N.
(b) Weight of elephant = 40000N
Area of one foot = 1000 cm
2
=1000×10
−4
m
2
Pressure=
Area
Force
Pressure=
1000×10
−4
40000
=400000N/m
2
(c) Weight of the girl = 400N
Area of heel of girl =1 cm
2
=1×10
−4
m
2
Pressure=
Area
Force
Pressure=
1×10
−4
400
=4000000N/m
2
(d) Girl exerts a larger pressure on the ground.
(e) Ratio =
Pressure exerted by the elephant
Pressure exerted by the girl
=
400000
4000000
=
1
10
The pressure exerted by girl is 10 times greater than that exerted by the elephant.