WEEK 3
POTENTIAL AND KINETIC ENERGY
Potential energy is the type of energy possessed by a body due to its position.A stone on the ground does not have energy so long as it is lying on the ground.The stone cannot be seen doing any work.However,if a stone is n a table and it placed on a table and it falls off,it can break a lamp on which it falls,the stone has done some work by virtue of its position.Therefore,when the stone is on the table,it has energy stored up as a result of its position.This energy increases as the height of the table increases and it decreases as it falls towards the ground.When it reaches the ground ,it has zero potential energy.
KINETIC ENERGY
This is the energy possessed by a moving body.For example,a moving car, a man running, a falling orange, a fired bullet,a rolling ball and so on all possess kinetic energy.Both forms of energy are examples of a more general forms of energy called MECHANICAL ENERGY.
KINETIC ENERGY
Kinetic energy(K.E) is the energy possessed by an object due to its motion i.e movement energy √K.E=1/2mv2
Where M is the mass of the moving object
V is the velocity of the object.
Potential energy is the energy possessed by an obect by virtue of its position at rest ( its height).Potential energy is stored energy.
P.E=m.g.h
M is mass of the object;
g is acceleration due to gravity; and
h is the height of the object from the ground.
Example1
If the mass of an object is 6kg and the height is 5m.Calculate the potential energy .(Assuming g=10m/s2)
Solution
P.E=m.g.h
M=6k.g
h=5m
g=10m/s2
P.E=6x5x10
=300J
Example 11
If the kinetic energy of a ball moving at a velocity of 10m/s2 is 50KJ.What is the mass of the ball?
Solution
K.E=1/2mv2
K.E=50KJ=50,000J
Velocity=10m/s2
50,000=1/2x mx102
i.e 50,000=1/2x 100m
=1/2x100m
50,000=50m
50m==50,000
M=50,000/50
=1000Kg
EVALUATION
1.Energy is measured in ————— while distance is measured in ———-
2.Mgh is a mathematical formula in basic science that is used to calculate ———–in a body
3.The energy possessed by a body by virtue of its position is called
a.potential b.Kinetic c.Food d.Muscular
SECTION B
1.Explain the meaning of the following.
i.Potential Energy ii. Kinetic Energy.
2.What type of energy does the sun transmit to the earth?
b.If a force of 50N is used to move an object through 20metres within 5seconds,Calculate the power of the object.
2c. A man of mass 90kg is moving at a constant velocity.He has kinetic energy of 2205J.Calculate the velocity at which he moves.