Physics
A spring is kept compressed by a small trolley of mass 0.5 kg lying on a smooth horizontal surface as shown. When the trolley is released, it is found to move at a speed of v = 2 ms-1. What potential energy did the spring possess when compressed?
Related Questions
How much energy is gained by a box of mass 20 kg when a man
(a) carrying the box waits for 5 minutes for a bus?
(b) runs carrying the box with a speed of 3 ms-1 to catch the bus?
(c) raises the box by 0.5 m in order to place it inside the bus?
(g=10 ms-2)
A bullet of mass 50g is moving with a velocity of 500ms-1. It penetrates 10 cm into a still target and comes to rest.
Calculate:
(a) the kinetic energy possessed by the bullet, and
(b) the average retarding force offered by the target.
Natasha is being constantly scolded by her mother for being unfit. She decides to loose weight by lifting a mass of 10 kg by 0.5 m 100 times. Assuming that the potential energy lost each time during the lowering of mass is dissipated.
Calculate :
(a) work done by her against the gravitational force.
(b) If fat stored in her body supplies 3.8 x 107 J of energy per kg, and is converted to mechanical energy with 20% efficiency, how much fat is used by Natasha
According to the principle of conservation of mechanical energy :
- Potential energy of a system is always greater than its kinetic energy
- Kinetic energy of a system is always greater than its potential energy
- Mechanical energy is always converted into heat energy
- Total mechanical energy of a system remains constant if no external force is worked on it.