Important Diagrams: Gravitation | Science Class 9 PDF Download

Q1: Answer the following questions based on the diagram given below:

(i) What is the motion of the stone in the given experiment?
Ans: The stone is moving in a circular path with a constant magnitude of velocity.

(ii) What happens to the stone's velocity as it moves along the circular path?
Ans: The stone's velocity changes direction at every point along the circular path, resulting in a variable velocity.

(iii) What force is responsible for making the stone move in a circular path?
Ans: The centripetal force, directed towards the center, is responsible for keeping the stone in a circular path.

(iv) What occurs when the thread holding the stone is released?
Ans: When the thread is released, the stone no longer experiences the centripetal force and flies off along a tangent to the circular path.

(v) How is the direction of the stone's motion affected when the thread is released?
Ans: The stone's direction of motion changes from circular to a straight line tangent to the circular path when the thread is released.

Q2: Answer the following questions based on the diagram given below:

(i) What is the gravitational force between two uniform objects directed along?
Ans: The gravitational force between two uniform objects is directed along the line joining their centers.

(ii) How does the distance between the centers of two uniform objects affect the gravitational force between them?

Ans: The gravitational force between two uniform objects increases as the distance between their centers decreases.

(iii) Is the gravitational force between two uniform objects affected by their mass?
Ans: Yes, the gravitational force between two uniform objects is directly proportional to their masses.

(iv) If the masses of two uniform objects are doubled, how does it affect the gravitational force between them?
Ans: If the masses of two uniform objects are doubled, the gravitational force between them also doubles.

(v) How is the direction of the gravitational force between two uniform objects determined?
Ans: The direction of the gravitational force between two uniform objects is along the line joining their centers.

Q3: Answer the following questions based on the diagram given below:

(i) Why does the iron nail sink when placed on the surface of water?
Ans: The iron nail sinks because its density is greater than that of water, causing the downward force of gravity to be greater than the upward buoyant force.

(ii) Why does the cork float when placed on the surface of water?
Ans: The cork floats because its density is less than that of water, resulting in the upward buoyant force of water being greater than the weight of the cork.

(iii) What is density, and how is it related to an object's ability to float or sink in a liquid?
Ans: Density is defined as the mass per unit volume of a substance. If the density of an object is less than the density of the liquid it is placed in, the object will float. Conversely, if the density of the object is greater than the density of the liquid, the object will sink.

(iv) Explain the role of gravitational force and upthrust of water in determining whether an object sinks or floats.
Ans: Gravitational force pulls an object downwards, and if this force is greater than the upthrust or buoyant force exerted by the liquid, the object will sink. If the upthrust is greater, the object will float.

(v) How does the experiment demonstrate the relationship between density and an object's behavior in a liquid?
Ans: The experiment shows that an object sinks or floats based on its density compared to the density of the liquid. Objects with greater density than the liquid sink, while those with lesser density float.

Q4: Answer the following questions based on the diagram given below:

(i) What does the experiment demonstrate regarding the elongation of the rubber string when the stone is suspended in the air?
Ans: The experiment shows that the rubber string elongates due to the weight of the stone when it is suspended in the air.

(ii) How does the elongation of the rubber string change when the stone is gradually immersed in water?
Ans: The elongation of the rubber string decreases as the stone is gradually immersed in water.

(iii) Why does the elongation of the rubber string decrease as the stone is immersed in water?
Ans: The decrease in elongation occurs because an upward force, known as buoyant force, is exerted on the stone by water, opposing the stone's weight.

(iv) Define Archimedes' principle based on the experiment.
Ans:  Archimedes' principle states that when a body is fully or partially immersed in a fluid, it experiences an upward force (buoyant force) equal to the weight of the fluid displaced by the body.

(v) What factors determine the magnitude of the buoyant force experienced by a body immersed in a fluid?
Ans: The magnitude of the buoyant force is determined by the volume of the body immersed in the fluid and the density of the fluid. It is not the same in all fluids for a given body, and different bodies experience different buoyant forces in a given fluid depending on their volume and density.