High School Physics + more

# Acceleration Numericals Class 9

In this post, we will solve a set of numerical problems based on the acceleration formula and related concepts (for class 9 students).

Formulas Used

1) Acceleration = change in velocity/duration of time
2) Acceleration = force/mass

Acceleration Numericals for class 9

1 ) A car is moving with a velocity of 30 m/s. The driver accelerated it for 5 seconds and reached a velocity of 40 m/s. What is the acceleration?

Solution:
Initial velocity = 30 m/s and final velocity is 40 m/s.
And the elapsed time = 5 seconds
Therefore, acceleration a = change in velocity/elapsed time = (40 -30) / 5 m/s2 = 2 m/s2

2 ) A car is moving with a velocity of 30 m/s. The driver applied brake for 3 seconds to bring it down to zero. What is the value of acceleration? Is it retardation?

Solution:
Initial velocity =30 m/s and final velocity is 0 m/s.
And the elapsed time = 3 seconds
Therefore, acceleration a = change in velocity/elapsed time = (0-30) / 3 m/s2 = -10 m/s2

So, acceleration = -10 m/s2
The negative value of a tells that it’s actually retardation.

3 ) An automobile manufacturer decides to build a car that can accelerate uniformly from 0 to 27 m/s in 10 s. The car’s mass is to be about 1,000 kilograms. What is the force required?

Solution:
First, we must determine the acceleration and then use Newton’s second law to find the force.

acceleration a = change in velocity/elapsed time = (27-0)/10 m/s2 = 2.7 m/s2

So the force needed to cause this acceleration is:
F = ma = 1,000 x 2.7 N = 2,700 N

4 ) A 10 N force is applied on an object of 10 kg. What will be the acceleration of the object?

Solution:
Given, Force F =10 N
Mass = m = 10 kg
So, acceleration a = F/m = 10/10 m/s2 = 1 m/s2