Force Numericals Class 8 - PhysicsTeacher.in

Last updated on July 6th, 2023 at 11:03 am

In this post, we will solve a set of Force Numerical problems for class 8 students. In the next section, you will find a set of formulas that are used to solve basic numerical problems of force.

Formula Used

F = ma
=> force = mass x acceleration

acceleration = (v-u)/t

acceleration = force/mass

Force Numericals for Class 8 with solution

Question 1) Calculate the force required to change the velocity of an object of mass 4 kg from 2 m s-2 to 4 m s-2 in one second.

Solution:

We will use this force formula, F = ma

mass m = 4 kg

acceleration a = (4-2)/1 m/s² = 2 m/s²

So the force, F = ma = 4 x 2 Newton = 8 N

Question 2) An object of mass 10 kg is moving with an initial velocity of 2 m s^-1.To make it come to rest in one second, what should be the unbalanced force?

Solution:

mass m = 10 kg.

initial velocity = 2 m s^-1
Velocity at rest = 0 m s^-1
time interval = 1 second,
Change in velocity in one second or acceleration = (0-2)/1 m/s² = – 2 m/s²
This negative sign means its retardation.

Force = mass x acceleration = 10 x (-2) N = -20 N
The negative sign means the force is acting opposite to the direction of motion.

Question 3) An object of mass 20 kg is moving with an initial velocity of 2 m s^-1. If its velocity changes to 4 m s^-1 in one second, what should be the force acting on it? What will be the direction of the motion?

Solution:

Force F = ma

mass m = 20 kg

acceleration a = (4-2)/1 m/s² = 2 m/s²

So the force, F = ma = 20 x 2 Newton = 40 N

The object continues to move in the same direction as the force applied is in the same direction of the motion.

Practice Problems | Extra numerical questions

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