Physics
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
Answer
It remains constant
Reason — As the skater glides across the ice, he possess kinetic energy due to his movement. The potential energy remains constant as there is no significant change in height. Assuming a smooth ice surface with no friction or air resistance, the external forces are absent, hence, according to the principle of conservation of mechanical energy, the total mechanical energy (KE + PE) of the skater remains constant.
Related Questions
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.
A spring is compressed storing potential energy. When the spring is released it propels an object forward. What change would you notice in the total mechanical energy of the system?
- It increases
- It decreases
- It becomes zero
- It remains constant
A a body is released from a height. During its motion in striking the ground, the quantity which does not change is:
- momentum
- kinetic energy
- potential energy
- mechanical energy