1. Give scientific reasons.
a. When an object falls freely to the ground, its acceleration is uniform.
b. Even though the magnitudes of action force and reaction force are equal and their directions are opposite, their effects do not get cancelled.
c. It is easier to stop a tennis ball as compared to a cricket ball, when both are travelling with the same velocity.
d. The velocity of an object at rest is considered to be uniform.
Answers
Answer:
a.when an object falls freely to the ground its acceleration is uniform. Where G is gravitational constant, M is mass of earth, R is radius of earth
b.when an object falls freely to the ground its acceleration is uniform. Where G is gravitational constant, M is mass of earth, R is radius of earth
c and d I don't know
Answer:
answer a. when any object falls freely to the ground its acceleration is constant since in a free fall, acceleration does not depend on the mass of This uniform acceleration is due to gravitational force of attraction of the earth which is constant for everything on earth, hence this acceleration is uniform, if air resistance is taken negligible.
acceleration due to gravity = 9.8 m/s×s
answer b. because action and reaction act on different bodies. for example when you push a wall action is your muscular strength pushing the wall, and the reaction is not done by you, since you yourself cannot act and react at the same time, hence here the resistive force of the wall acts as reaction force, because if the wall would apply no resistive force it will break. both action and reaction act on different objects so that they do not get cancelled.
answer c. momentum = mass × velocity
when you keep the velocity of tennis ball and the cricket ball constant the momentum then surely depends on mass.
so its understood that mass of tennis ball is less than the mass of cricket ball and therefore the momentum of tennis ball is less than the momentum of cricket ball. hence its easier to catch the tennis ball.
answer d. uniform means constant or something which cannot be changed.
now for a body at rest its speed is zero all the time since its not moving. velocity = displacement/time , displacement = final position- initial position
now for body at rest,
initial position = a (lets assume)
final position = a (since the body is not moving)
let time be n seconds
so now velocity = a-a/n
velocity = 0/n= 0 ( for all cases where body is at rest.