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Physics Work, Energy and Momentum:
Energy and Work:
When an object is moved using a force, work is done on the object by the
Work Done = Energy Transferred
The work done depends on the size of the force and the distances moved.
Work Done(J) = Force(N) x Distance moved in direction of force(m)
Eg.) If a weightlifter lifts a weight of 200N to a height of 1.5m, how much
work is done?
A) 200N x 1.5m = 300J.
Work Done to overcome friction is mainly transferred into heat energy.
The kinetic energy of an object is the energy it has due to its movement.
This depends on the mass and the speed of the object.
Kinetic Energy = ½ x mass x speed2
If you double the speed, the kinetic energy quadruples.
The heavier the ball and the quicker the speed, the more kinetic
Elastic Potential Energy:
Elastic potential energy is the energy stored in an object when work is done
to change its shape
Momentum(Kgm/s) = Mass(Kg) x Velocity(m/s)
Momentum is conserved when objects interact, provided that there are
no external forces acting.
The Total Momentum before a collision is equal to the total
momentum after a collision.
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Eg.) If a 0.8kg gun fires a 0.05Kg bullet at 400m/s, at what speed does
the Gun recoil?
Momentum = 0.05 x 400
(Mass of A x Velocity of A) = (Mass of B x Velocity of B)
Change in Momentum
Force(N) = Change in momentum(Kgm/s) F = force
Time(s) m = mass
V = final velocity
F = mv mu u = start velocity
t t = time
Making the time longer decreases the size of the force.…read more