Physics
Assertion (A) : A swimmer pushes the water backward to move forward in a swimming pool.
Reason (R) : Water exerts a greater but opposite force on the swimmer, helping him to move forward.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Answer
assertion is true but reason is false
Explanation
Assertion (A) is true because when a swimmer wants to move forward in water, he pushes the water backward using his hands and feet which is an action force so according to Newton’s third law of motion : "for every action, there is an equal and opposite reaction", the water pushes back on the swimmer with an equal force in the opposite (forward) direction. This reaction force is what actually propels the swimmer forward.
Reason (R) is false because water exerts an equal and opposite force (not greater), according to Newton’s third law of motion.
Related Questions
Assertion (A) : If the distance between bodies of masses M1 and M2 is increased by a factor of 4, the gravitational force reduces by 1/16.
Reason (R) : The gravitational force is inversely proportional to the square of distance between two bodies.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Assertion (A) : Weight is the force with which the earth attracts a body.
Reason (R) : It is a measure of the quantity of matter contained in the body, at rest.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
In a supermarket, Avantika could easily push an empty trolley but found it difficult to push a trolley full of groceries. The loaded trolley accelerated very slowly even when the same force was applied. To keep the trolley moving, she had to apply a greater force.
(a) Why did the loaded trolley accelerate less?
(b) According to you, which law of motion explains this observation?
(c) Why did Avantika have to apply a greater force to the loaded trolley?
(d) Correlate this event with one other similar example from daily life.
During the annual sports day, a game of tug of war was held. The two teams pulled the rope in opposite directions. Although the rope did not move initially for two minutes, both teams felt a strong pulling force.
(a) Why did both teams feel a pull?
(b) Which law of motion comes into play in the above situation?
(c) Name the forces acting in this situation.
(d) State two other examples of this force.