A man drop a stone of mass 2kg room the top of a building of height 15m when it reaches the ground find its kinetic energy.
K.E=initial P. E
:K.E=mgh
K.E=2*15*9.8
K.E=294
KE=initial PE=2*9.8*15 joules
According to law of conservation of energy potential energy of an object at the height is transfer is kinetic energy increases the ground
m=2kg
h=15m
g=10m/s
Kinetic energy=mgh
=2×10×15
=300J
Well, let's hope the stone didn't hit anyone on the head! Anyway, to calculate the kinetic energy, we need to use the formula:
Kinetic Energy = 0.5 * mass * velocity^2.
Now, we know the mass of the stone is 2kg, but we don't have the velocity. However, we can find it using the equation for gravitational potential energy. The potential energy at the top of the building is equal to the kinetic energy at the bottom, since there is no loss of energy due to friction or air resistance.
So, let's calculate the potential energy first. The potential energy is given by:
Potential Energy = mass * gravity * height.
Plugging in the values, we get:
Potential Energy = 2kg * 9.8m/s^2 * 15m = 294 Joules.
Since potential energy is equal to kinetic energy at the bottom, we can solve for the velocity. Rearranging the formula, we get:
Kinetic Energy = 0.5 * mass * velocity^2.
294 Joules = 0.5 * 2kg * velocity^2.
Simplifying:
294 Joules = 1kg * velocity^2.
Dividing both sides by 1kg, we get:
294 Joules / 1kg = velocity^2.
Finally, taking the square root of both sides of the equation:
Velocity = √(294 Joules / 1kg).
Calculating this, we find:
Velocity ≈ 17.14 m/s.
So, the kinetic energy of the stone when it reaches the ground is approximately 294 Joules.
To find the kinetic energy of the stone when it reaches the ground, you can use its potential energy at the top of the building and the principle of conservation of energy.
The potential energy (PE) of an object is given by the formula:
PE = m * g * h
where 'm' is the mass of the object, 'g' is the acceleration due to gravity (approximately 9.8 m/s²), and 'h' is the height above the reference point.
In this case, the height 'h' is 15m and the mass 'm' is 2kg. So, the potential energy of the stone at the top of the building is:
PE = 2kg * 9.8 m/s² * 15m = 294 Joules
According to the principle of conservation of energy, this potential energy will be converted to kinetic energy (KE) when the stone reaches the ground. Therefore, the kinetic energy of the stone when it reaches the ground will also be 294 Joules.