Kinetic energy is the energy possessed by an object due to its motion. The faster an object moves, the more kinetic energy it has.
The formula for kinetic energy (KE) is given by:
KE=1/2mv2
Where:
The standard unit of kinetic energy is the joule (J).
An athlete with a mass of 70 kg running at 8 m/s:
KE=1/2×70 kg×(8 m/s)2=2240 J
A ball with a mass of 0.5 kg rolling at 10 m/s:
KE=1/2×0.5 kg×(10 m/s)2=25 J
A bicycle with a mass of 15 kg moving at 6 m/s:
KE=1/2×15 kg×(6 m/s)2=270 J
A pendulum bob with a mass of 0.2 kg swinging at 2 m/s:
KE=1/2×0.2 kg×(2 m/s)2=0.2 J
A skater with a mass of 60 kg moving at 12 m/s:
KE=12×60 kg×(12 m/s)2=4,320 J
tennis ball with a mass of 0.06 kg served at 40 m/s:
KE=1/2×0.06 kg×(40 m/s)2=48 J
An object with a mass of 5 kg falling at 9.8 m/s2 (acceleration due to gravity):
KE=1/2×5 kg×(9.8 m/s)2=240.1 J
A skateboarder with a mass of 75 kg jumping with a velocity of 5 m/s:
KE=12×75 kg×(5 m/s)2=937.5 J
A bullet with a mass of 0.01 kg fired at 500 m/s:
KE=12×0.01 kg×(500 m/s)2=125 J
| Numbering | Questions | Answers |
|---|---|---|
| 1. | What is the formula for kinetic energy? | KE=1/2mv2 |
| 2. | Define kinetic energy in your own words. | Kinetic energy is the energy an object possesses due to its motion. |
| 3. | What are the units of kinetic energy? | Joules (J) |
| 4. | If the mass of an object is 2 kg and its velocity is 4 m/s, calculate its kinetic energy. | KE=1/2×2 kg×(4 m/s)2=16 J |
| 5. | How does the kinetic energy of an object change if its velocity is doubled? | Kinetic energy increases four times (quadruples). |
| 6. | If the velocity of an object is zero, what is its kinetic energy? | Kinetic energy is zero. |
| 7. | Explain the relationship between mass and kinetic energy. | Kinetic energy is directly proportional to the square of the velocity and the mass of an object. |
| 8. | A skateboarder with a mass of 60 kg is moving at 8 m/s. Calculate the kinetic energy. | KE=1/2×60 kg×(8 m/s)2=1,920 J |
| 9. | How does kinetic energy change with an increase in mass while keeping the velocity constant? | Kinetic energy increases linearly with an increase in mass. |
| 10. | What happens to the kinetic energy of a car if its velocity is halved? | Kinetic energy decreases to one-fourth of the original value. |
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