When a car travelling at an initial velocity of 10 m/s applies the brakes and bring ... accelerates from rest for a time of 8 seconds with an acceleration of 3.2m/s^2?
Answer: 
Explanation:
Given
mass of ball m=10 kg
It is placed at a height of 150 m
It is dropped from the height and allowed to free fall for 40 m
Velocity acquired by the ball during this fall is given by 
Insert u=0, a=g
Kinetic energy at this instant
Answer:
Explanation:
Given
mass of stone
=0.250 kg
Let initial velocity with which it is thrown upward is u
therefore after time t it's velocity is zero at highest point
t=
where g= gravity at earth
therefore 
-------1
Now same thing is done in Planet X where gravity is g'
therefore time taken by stone to reach surface is
-------2
Divide 1 & 2
=
=
g'=
Answer:
a. negative
b. zero
Explanation:
work is the change in the energy of a system due to external forces
work is done when a force moves a load through a distance in the direction of the force
The work done by a force on a system is positive when the force and the force displacement point in the same direction and negative when they point in opposite directions
in the scenario we are considering in the question, the force (the hand) moves the block vertically upwards but the displacement of the block reduces (in the opposite direction) since it decelerates. as such the work done by gravity on the block is negative.
the work done on the block is zero if the system consists of the block and the earth because there is no gravitational force exerted on the system
