Advertisements
Advertisements
Question
A metal ball of mass 5 kg falls from a height of 490 m. How much time it will take to reach the ground? (g = 9.8 m/s2)
Advertisements
Solution
Given, Mass (M) = 5 kg.
Distance travelled by the ball (s) = 490 m
Initial velocity of the ball (u) = 0
Gravitational acceleration (g) = 9.8 m/s2
Newton's second equation of motion gives
s = `"ut" + 1/2 "gt"^2`
∴ 490 = `0 xx "t" + 1/2 xx 9.8 xx "t"^2` .....[Initial velocity (u) = 0]
⇒ 490 = 4.9 t2
t2 = `490/4.9`
t2 = 100
t = 10 sec.
∴ The ball takes 10 seconds to reach the ground.
APPEARS IN
RELATED QUESTIONS
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet.
A ball thrown up vertically returns to the thrower after 6 s. Find
- the velocity with which it was thrown up,
- the maximum height it reaches, and
- its position after 4 s.
State whether the following statement is true or false :
A falling stone also attracts the earth.
State whether the following statement is true or false :
The acceleration due to gravity acting on a freely falling body is directly proportional to the mass of the body.
Give reason for the following :
The force of gravitation between two cricket balls is extremely small but that between a cricket ball and the earth is extremely large.
What do you understand by the term 'acceleration due to gravity of earth' ?
Why does a sharp knife cut objects more effectively than a blunt knife ?
Explain why, a wide steel belt is provided over the wheels of an army tank.
Explain why, the tip of a sewing needle is sharp.
A stone is thrown vertically upwards with initial velocity u reaches a height ‘h’ before coming down. Show that the time taken to go up is the same as the time taken to come down.
The acceleration produced in a body by a force of given magnitude depends on
How is the acccelaration due to gravity on the surface of the earth realted to its mass and radius ?
How are g and G realated ?
A body is projected vertically upward with an initial velocity u . If acceleartion due to gravity is g , the time for which it remains in air , is :
What force, in newton, your muscles need to apply to hold a mass of 5 kg in your hand? State the assumption.
Distinguish between:
Universal gravitational constant - Gravitational acceleration of earth.
The mass and weight of an object on earth are 5 kg and 49 N respectively. What will be their values on the moon? Assume that the acceleration due to gravity on the moon is 1/6th of that on the earth.
Calculate the escape velocity on the surface of the moon given the mass and radius of the moon to be 7.34 × 1022 kg and 1.74 × 106 m respectively.
(Given: G = 6.67 × 10-11 Nm2/kg2)
When is free fall possible?
