Kinetic Energy 1

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Kinetic Energy 1

When an object is moving, it is said to have KINETIC ENERGY.
The faster it moves, the greater is its kinetic energy.

Think about this :
If you throw a small stone at a window pane at a slow speed, the window would not break.
However, if you throw the very same stone at a high speed, the window would break!

The extra speed gives the stone a greater KINETIC ENERGY.

Some Facts
a. Kinetic Energy is the energy an object has as a result of its speed.
b. Kinetic energy, like all other forms of energy, is measured in joules (J).
c. Kinetic energy is a scalar quantity. You do not include direction in your answer for kinetic energy.
d. The symbol for Kinetic Energy is E_K.

KINETIC ENERGY FORMULA
E_K=½mv²
E_K is KINETIC ENERGY
m is the mass
v is the speed

Examples
1. The speed of a 4kg trolley is 3ms^-1. Calculate the kinetic energy.
E_K=½mv²
E_K=½(4)(3)²
E_K=18J

2. The kinetic enery of a 6kg trolley is 12J. Calculate its speed.
E_K=½mv²
12 = ½(6)v²
12 = 3v²
4 = v²
v= 2ms^-1

3. The kinetic energy of cart is 20J. Calculate the mass of the cart if it is moving at 4ms^-1.
E_K=½mv²
20 = ½m(4)²
40 = m16
m = 2,5kg