High School Physics

# Thrust and Pressure Numericals for class 9 [solved]

Last updated on June 25th, 2023 at 01:29 pm

In this post, we have solved a set of Thrust and Pressure Numericals for class 9. Before that, we will go through the formulas used to solve these force and pressure problems.

Formulas Used

Pressure P = F/A = Force in perpedicular direction / Area

Pressure P = Thrust / Area

Force or thrust = Pressure x Area
=>F = PA

Thrust and Pressure Numericals for class 9 [with solution]

(Q1) Calculate the pressure exerted by a dancer weighing 600N standing on a single heel of area 1 cm2. The surface of the dance floor is broken by pressures over 5 MPa. Will it be damaged by the dancer?

Solution:

Force F = 600 N

Area A = 1 cm2 = 0.0001 m2

Pressure P = F/A
P = 600/0.0001 Pa = 6 x 106 Pa = 6 MPa.

Answer: As the pressure exerted by the dancer is 6 MPa, which is more than the limit provided (5 MPa), hence the dance floor will be damaged by the dancer.

(Q2) What pressure is exerted by a force of 50000 N acting on 2.5 m2?

Solution:

Force F = 50000 N

Area A = 2.5 m2

Pressure P = F/A
P = 50000/2.5 Pa = 20000 Pa

Force and Pressure Numericals for class 9

(Q3) A swimming pool has a level, horizontal, bottom. Its dimensions are 25 m by 5 m. The pressure of the water on the bottom is 15000 Pa. What total force does the water exert on the bottom of the pool? What is the weight of water?

Solution:

Area A = 25×5 = 125 m2
Pressure P = 15000 Pa.
So, the total force exerted on the bottom of the pool:
F = PA = 15000 x 125 = 1875 x 103 N
The weight of water is also 1875 x 103 N

(Q4) An elephant has a mass of 5000 kg. The area of an elephant’s foot is 0.13 m2. A woman has a mass of 60 kg. The area of her heel is 25 mm2. Calculate the pressures exerted by the elephant and the woman.

Solution:

In the case of the Elephant:
mass = 5000 kg
area of foot = 0.13 m2

Weight of the elephant = thrust = 5000 x 10 N = 50 000 N
Total area of 4 feet of the elephant = 4 x 0.13 m2 = 0.52 m2

Hence, Pressure exerted by the elephant = thrust / area = 50000 / 0.52 = 96154 Pa

In the case of the woman:
mass =60 kg
area of foot = 25 mm2 = 25 x 10-6 m2

Weight of the woman = thrust = 60 x 10 N = 600 N
Total area of 2 feet of the woman = 2 x 25 x 10-6 m2 = 50 x 10-6 m2

Hence, Pressure exerted by the woman = thrust / area = 600 / [50 x 10-6] = 12 x 106 Pa = 12 MPa

Also, solve these Pressure Practice Problems

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