Physics
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
Related Questions
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.
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?
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.
A skater is gliding on a smooth ice surface. What happens to his mechanical energy as he skates?
- It increases
- It decreases
- It becomes zero
- It remains constant