class 9 physics chapter 10 ncert solutions
Answers
Q1: Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth.
A: Consider F is the force of attraction between an object on the surface of earth and earth.
Also, consider ‘m’ is the mass of the object on the surface of the earth and ‘ Me’ is the mass of earth.
∴ The formula for magnitude of the gravitational force between the earth and an object on the surface is given as:

Q2: State the universal law of gravitation.
A: 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.
Q3: What do you mean by acceleration Q due to gravity?
A: When an object falls freely from a certain height towards the earth’s surface, its velocity changes. This velocity change produces acceleration in the object known as acceleration due to gravity, represented by the letter g.
The gravity-based acceleration value is,

Q4: What are the differences between the mass of an object and its weight?
A: The differences between the mass of an object and its weight are tabulated below:

Q5: Why is the weight of an object on the moon 1/6th its weight on the earth?
A: The moon’s mass is 1/100 times and 1/4 times the earth’s radius. As a result, when compared to earth, the gravitational attraction on the moon is about one-sixth. Thus, an object’s weight on the moon is 1/6th its earth weight.
Q6: What do you mean by buoyancy?
A: The upward force possessed by a liquid on an object that’s immersed in it is referred to as buoyancy.
Q7: You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why?
A: The bag of cotton is heavier than the bar of iron. The cotton bag has a larger air thrust than the iron bar. The weighing machine, therefore, indicates a smaller cotton bag weight than its actual weight