# NCERT Class 9 Science Solutions: Chapter 10 – Gravitation Part 1

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Question 1:

Q. State the universal law of gravitation

**Answer:**

The universal law of gravitation states that every object in the universe attracts every other object with a force called the gravitational force. The force acting between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

For two objects of masses and and the distance between them the force of attraction acting between them is given by the universal law of gravitation as:

Where, is the universal gravitation constant given by:

Question 2:

Q. Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth.

**Answer:**

Suppose the earth is a sphere of mass M and radius R and if an object of mass m is placed on the surface of the earth, then the magnitude of the gravitational force between the body and the earth will be:

Question 1:

Q. what do you by free fall?

**Answer:**

Gravity of the Earth attracts every object towards its centre. when an object is released from a height, it falls towards the surface of the Earth under the influence of gravitational force. The motion of the object is said to have free fall.

Question 2:

Q. What do you mean by acceleration due to gravity?

Answer:

When an object falls towards the ground from a height, then its velocity changes during the fall. This changing velocity produces acceleration in the object. This acceleration is known as acceleration due to gravity. Its value is given by