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Subject Summarize - Coggle Diagram
Subject Summarize
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Work, Power and Energy
Work is a scalar quantity that tells how efficient a force is in order to move an object along the force.
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Power is a quantity that tells how much work is done in a unit of time. The unit for power is watt.
P = W/Δt
Energy is a scalar quantity that tells the ability to work or change the movement. In mechanics, there are two types of energy, which is kinetic energy and potential energy
Consider work by the force F that moves an object of mass m on smooth surface from initial speed u to final speed v with constant acceleration.
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Consider work by gravity acting on an object of mass m. The gravity moves the object from height hA to hB.
We define this term as the gravitational potential energy (Epg). An object of mass m at height h from reference point, the energy is
Epg = mgh
Work equation: Wg = - ΔEpg
Consider work by spring force that moves an object of mass m attached to the spring from x=xA to x=xB. Given that the spring constant is k.
We define this quantity as elastic potential energy (Eps). An object that is attached to a spring with spring constant k and is x away from the resting point has potential energy
Eps = 1/2kx(squared)
Work equation: -ΔEps
Equilibrium
Equilibrium is a state of an object where there is no total force acting on the object. There are two type of equilibrium, which are: Translational Equilibrium (Linear) and Rotational Equilibrium (Angular)
The center of mass is the point where we consider whether the movement around that point is at equilibrium or not.
Another definition is that when there is force acting on the center of mass of the object, it only changes the translational movement, but not rotational movement.
The center of mass is the same as the center of gravity. They are only different when there is an uneven distribution of gravity.
*The center of mass does not need to be inside of the object.
Translational: to be at equilibrium the object has to have 0 net force acting on it.
v = constant
a = 0
F = ma = 0
Rotational equilibrium is the state of object or system that does not rotate or rotate with constant angular speed.
In order to stay at rotational equilibrium, the clockwise and counter-clockwise moments of the object/system has to be equal:
MCL = MCC
Momentum and Collision
Momentum is a vector quantity that determines the object's potential in collision or explosion. It is defined as the product between mass and velocity
P = mv
In the case of a system where there is force that changes the movement of an object, we can find the relation between force and momentum as follows.
F = Δp/Δt
The collision/explosion that preserves both energy and momentum is said to be elastic collision/explosion
If it only preserves momentum, it is said to be non-elastic collision/explosion