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Kinetic Energy

Energy is the currency of transformation. All systems remain the same unless energy is exchanged between one part and another. Learn here about the energy associated with movement.

Kinetic energy of an object

A $$14\text{ kg}$$ object initially at rest starts to fall freely. If air resistance is negligible, what is the object's kinetic energy after $$0.5$$ seconds?

The gravitational acceleration is $$g=10\text{ m/s}^2.$$

What is the kinetic energy of a $$6\text{ kg}$$ object moving at $$10\text{ m/s}?$$

A car of mass $$1900\text{ kg}$$ is traveling at $$28\text{ m/s}$$ on a street that has a speed limit of $$20\text{ m/s}.$$ The driver spots a police car and reduces its speed to match the speed limit. How much kinetic energy did the car lose?

A $$10\text{ kg}$$ object, $$A$$, travels at $$6\text{ m/s},$$ and a $$6\text{ kg}$$ object, $$B$$, travels at $$10\text{ m/s}.$$

Find the ratio $$\text{K.E.}_A/\text{K.E.}_B$$.

Recently, a meteor impacted Russia. The estimate of the meteor's size was $$10~\mbox{tons}$$ and it was estimated to have entered the earth's atmosphere at a speed of $$14,600~\mbox{m/s}$$. What was the total kinetic energy of such a meteor in J as it entered the atmosphere?

Details and assumptions

• One ton is $$907~\mbox{kg}$$.
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