High School Physics

Mass and Weight Numericals Class 9

In this post, we will solve mass and weight numericals based on the class 9 science (physics) syllabus. These numerical questions are based on the concepts of mass and weight and their relationship.

Formulas Used

1) weight of a body = mass of that body x acceleration due to gravity at that location
W =mg
2) Mass = weight/acceleration due to gravity at that location
=>m = W/g
3) g = W/m

Mass and Weight Numericals for Class 9 [solved]

Question 1] The mass of a body is 10 kg. What is its weight?

Solution.

The weight of a body is calculated by using the formula :
Weight, W = m × g
Here, the Mass of the body, m = 10 kg
And, Acceleration due to gravity, g = 9.8 m/s2
So, Weight, W = 10 × 9.8 = 98 N
Thus, the weight of the body is 98 newtons.

Question 2] What is the mass of an object whose weight is 490 newtons?

Solution.

Here, Weight, W = 490 N
Mass, m =? (To be calculated)
And, Acceleration due to gravity, g = 9.8 m/s2
Now, putting these values in the formula
W = m × g
we get : 490 = m × 9.8
m = 490/9.8
m = 50 kg
Thus, the mass of the object is 50 kilograms

Question 3] A man weighs 900 N on the Earth. What is his mass? (take g = 10 m s–2).
If he were taken to the moon, his weight would be 150 N. What is his mass on the moon?
What is the acceleration due to gravity on the moon?

Solution.

First of all, we will calculate the mass of man on the earth by using the formula: W = m × g
Here, the Weight of man on earth, W = 900 N
Mass of man on earth, m =? (To be calculated)
And, Acceleration due to gravity, g = 10 m s–2 (on Earth)
Now, putting these values in the above formula, we get :
900 = m × 10
So, m = 900/10
m = 90 kg
Thus, the mass of man on the earth is 90 kilograms.

Now, the mass of a body remains the same everywhere in the universe. So, the mass of this man on the moon will also be 90 kilograms.

We will now calculate the value of acceleration due to gravity on the moon by using the same formula :
W = m × g
Now, the Weight of man on the moon, W = 150 N
Mass of the man on the moon, m = 90 kg (Calculated above)
And, Acceleration due to gravity (on the moon), g =? (To be calculated)

By putting these values in the above formula, we get :
150 = 90 × g
So, g = 150/90
g = 1.66 m s–2
Thus, the acceleration due to gravity on the surface of the moon is 1.66 m s–2

Question 4] How much would a 100 kg man weigh on the moon? What would be his mass on
the Earth and on the moon? (Acceleration due to gravity on the moon = 1.63 m/s2)

Solution.

We will first calculate the weight of the man on the moon.
Here, the Mass of the man on the moon, m = 100 kg
Acceleration due to gravity (on the moon), g = 1.63 m/s2

We know that : W = m × g
So, W = 100 × 1.63 N
W = 163 N
Thus, the man would weigh 163 newtons on the moon.

The mass of a body is constant everywhere in the universe. So, the mass of this man would be the same on the Earth as well as on the moon, that is, the mass will be 100 kg on the Earth as well as on the moon.