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(New tips are continually added to these pages.  Check back in a few months' time for more)

TOPIC 3:    Conservation of Momentum and Energy

Tip 1:

Most students are familiar with elastic collisions, inelastic collisions and perfectly inelastic collisions.  But what about super elastic collisions?

Super elastic collisions are collisions in which the total Kinetic Energy of the system after the collision is greater than the total Kinetic Energy of the system before the collision.

Where does the additional energy come from?  It comes from stored forms of energy (potential energy).  Examples of such energy are gravitational potential energy, elastic potential energy, chemical energy, and nuclear energy.

For example, if I shoot a bullet at a stationary hand grenade, and the grenade explodes, the total K.E. of the system after the collision is greater than the total K.E. of the system before the collision.  In this case, the additional energy comes from the chemical energy of the explosives stored in the grenade.

Another example, when a neutron strikes a Uranium nucleus, resulting in fission reaction, the total Kinetic Energy of the daughter nuclei and neutrons produced exceeds the total Kinetic Energy of the reactants.

 

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