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If the suitcase falls off the cupboard, it will lose its potential energy. Halfway down the cupboard, the suitcase will have lost half its potential energy and will have only $\mathrm{9,8}\phantom{\rule{2pt}{0ex}}J$ left. At the bottom of the cupboard the suitcase will have lost all it's potential energy and it's potential energy will be equal to zero.
Objects have maximum potential energy at a maximum height and will lose their potential energy as they fall.
A brick with a mass of $1\phantom{\rule{2pt}{0ex}}\mathrm{kg}$ is lifted to the top of a $4\phantom{\rule{2pt}{0ex}}m$ high roof. It slips off the roof and falls to the ground. Calculate the potential energy of the brick at the top of the roof and on the ground once it has fallen.
All quantities are in SI units.
Since the block is being lifted we are dealing with gravitational potential energy. To work out $PE$ , we need to know the mass of the object and the height lifted. As both of these are given, we just substitute them into the equation for $PE$ .
Kinetic energy is the energy an object has due to its motion.
Kinetic energy is the energy an object has because of its motion. This means that any moving object has kinetic energy. The faster it moves, the more kinetic energy it has. Kinetic energy ( $KE$ ) is therefore dependent on the velocity of the object. The mass of the object also plays a role. A truck of $\mathrm{2\; 000}\phantom{\rule{2pt}{0ex}}\mathrm{kg}$ , moving at $100\phantom{\rule{2pt}{0ex}}\mathrm{km}\xb7\mathrm{hr}{}^{-1}$ , will have more kinetic energy than a car of $500\phantom{\rule{2pt}{0ex}}\mathrm{kg}$ , also moving at $100\phantom{\rule{2pt}{0ex}}\mathrm{km}\xb7\mathrm{hr}{}^{-1}$ . Kinetic energy is defined as:
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