A man drops a 10 kg rock from the top of a5m ladder. Calculate its energy when it reaches to the ground.Also calculate velocity
Answers
ANSWER :
Mass of the rock = 10 kg
Height from ground = 5 m
Acc.due to gravity = 9.8 m/s^2
NOTE : Kinetic Energy of the object before it touches the ground will be equal to potential energy, as the potential energy get converted to kinetic energy. So before it touches ground, all the potential energy gets converted to kinetic energy.
Potential Energy = m * g * h
Potential Energy = 10 * 9.8 * 5
Potential Energy = 490 J
Therefore, the energy of the rock before it touches the ground is 490 joules.
CALCULATING VELOCITY :
Initial Velocity ( u ) = 0
Final Velocity ( v ) = ?
Acc.due to gravity ( g ) = 9.8 m/s^2
Displacement ( s ) = 5 m
Use the 3rd equation of motion :
v^2 - u^2 = 2gh
=> v^2 - 0^2 = 2 * 9.8 * 5
=> v^2 = 98
=> v = ~9.9 m/s
Therefore, velocity before touching ground in 9.9 m/s
Hope this helps you☺☺