Class 8 Physics – Forces and Pressure Numerical Problems (Complete Bundle: Part 1, 2 & 3)

Title: FORCE & PRESSURE – NUMERICALS (Part : 1,2 & 3)

Question: 1

Find the moment of force of 20 N about an axis of rotation at a distance of 0.5 m from
the force.

Solution:

Given:
Force, F = 20 N
Distance d = 0.5 m

Formula:
Moment of Force (τ) = Force (F) × Distance (d)

Substitution:
τ = 20 × 0.5 = 10

Final Answer:
Moment of force, τ = 10 N·m

Question: 2

The moment of a force of 25 N about a point is 2.5 N·m. Find the perpendicular distance
of the force from that point.

Solution:

Given:
Moment of force, τ = 2.5 N·m
Force, F = 25 N
Perpendicular distance, d = ?

Formula:
τ= F x d
Rearrange Formula: d = τ / F

Substitution:

, d = 2. = 0.1 m

Conversion:
1 m = 100 cm
0.1 m × 100 = 10 cm

Final Answer:
Perpendicular distance = 10 cm

Question: 3

A spanner of length 10 cm is used to unscrew a nut by applying a minimum force of 5.0
N. Calculate the moment of force required.

Solution:

Given:
Length of spanner, d = 10 cm
Force applied, F = 5.0 N
Moment of force, τ = ?

Convert to meter:
10 cm = 0.1 m

Formula :
Moment of Force = Force x Distance
τ=Fxd

Substitution:
τ = 5 x 0.1 = 0.5 N m

Final Answer:
Moment of force = 0.5 N m