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Classical Mechanics

Kinetic Energy

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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