Newton's laws of motion
By kacheung chanThe First law
Other than exerting external force, mass will remain its state of uniform Linear velocity or static. It is known as inertia.The Second law
Let the initial and final velocityof the mass is U and V. Then,
The Third Law
When two mass collide together, both of them suffer from equal but inverse force. This is called action and reaction force.
The law of conservation of momentum
It is stated that within a enclosed isolated system, all momemtum will remain the same after a collision. As mentioned by Newton third law, two collision forces F1 and F2 are equal but reverse.
Initial monentum=final momemtum
some
Work, kinetic energy, potential energy and power
By ka cheung chanWork
When we lift up a load by a force for a certain distance. The work has been done.So that, work is the cross product of force and displacement and the vector direction is equal to the displacement.
The same priniciple can be applied to the spring. When it is elongated, it is same as the displacement. The work needed to lengthen the spring is
Or
Where the product is the area under the curve according to integration.
If initial velocity is not zero,
It is equal to the kinetic energy gained. In order to make more work done, more energy should provided.
Potential energy
Potential energy is the reverse or result of kinetic energy. When we lift up a load, a kinetic energy is used (work done), and a potential energy is being stored in this load. Similarly, a spring is being elongated by a force (kinetic energy), so a potential energy is stored inside pretended to expand outwards). The higher level the load was lift to, the more extent was the potential energy.Work done for lifting up a load = the work that the load act on the earth
= Fh
=mgh
Work done for stressing a spring = the work that stored inside the spring
K= kinetic energy
U= potential energy
E= total energy
Power
Power is the rate of work being done over a period of time.
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