Question

Answer the following



1.A stone of mass 500 gm is dropped from a certain height. When it is exactly at the midpoint of is free fall, the kinetic energy possessed by it is 800 J. what is the height from where it is dropped? (take acceleration
due to gravity of earth as 10m/s^2)

2.A car of mass 2, 000 Kg travelling with a uniform velocity of 2 m/s accelerates till its velocity becomes 22 m/s. The work done on the car is:

3.The engine of a bus of mass 5, 000 kg accelerate the bus from 2 m/s to 20 m/s in 120 seconds. The power
expended by the bus is:

4.From a tower of height 20 m a boy throws a stone in the vertically upward direction with a velocity of 40 m/s
and at the same time a girl drops another identical stone from the same tower. When the momentum of the
stone dropped by the girl is maximum what will be displacement of the stone projected in the upward direction from the top of the tower? (Take acceleration due to gravity of earth as 10 m/s^2)

5.A car driver travelling with a uniform velocity of 2m/s notices a railway level crossing at a distance of 435 m
from him. And also he notices that it is going to be closed in 10 seconds. First he decides to cross the level crossing hence he accelerates his car at the rate of 2 m/s^2 for five seconds. Then he decides to stop the
car. So he applies brake and stops the car exactly before the level crossing (without following the timer). Calculate the minimum rate at which he has to decelerate the car so that he stops the car exactly before the level crossing

6.Two cars X and Y accelerate at the rate of 2 m/ s^2and 3 m/s^2 respectively from rest. The ratio of time taken by the cars X and Y is 4: 5. In that given ratio of time interval if the distance travelled by car X is 100 km then the distance travelled by car Y is:

7.Two files A and B revolve around a light in concentric circular path. The radius of circular path of A is twice of B. A travels with a uniform linear speed of 4 m/s while B travels with a uniform linear speed of 3 m/s.
when A completes tree full rounds then B would have completed:

Answer 1

As

m = 500 gm = 0.5 kg

p.e. = 800 j

g = 10 m/s^2

potential energy = mass x acceleration due to gravity x height

800 = 0.5 x 10 x h

800/5 = h

∴ h = 160