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Tahsili Physics (Energy and Machines) Cheat Sheet by

2023 Tahsili Physics, energy and machines

System Types

open system
can gain and lose mass and energy
closed system
a system that does not gain nor lose mass
Isolated system
a sytem that does not exchange mass nor energy

Momentum and Impulse

impulse (I)
I or ΔP = FΔt
impulse unit
Location on a graph
under the Force - Time curve
P = mv
Law of Conser­vation Of Momentum
m1v1 + m2v2 = (m1+m2)v
in any closed or isolated system, the momentum is conserved
impulse is the change in momentum, so I = ΔP

Kinetic Energy

KE Formula
KE = (1/2)mv2
work-e­nergy theorem
work is equal to the change in KE ( W = KEf - KEi )

Potential Energy

Gravit­ational Potential Energy
energy stored as a result of the gravit­ational attraction of the earth on the object
PE = mgh
Elastic Potential Energy
the energy stored in elastic materials as a result of their stretching or compre­ssing


Simple Machine
a machine that makes work easier by changing the value of force or its direction
compound machine
a device that uses multiple simple machines
Mechanical advantage
Fr / Fe (resis­tance force / effort force)
Ideal Mechanical Advantage
de / dr (effort displa­cement / resistance displa­cement)
Compound Mechanical Advantage
the product of the MA of its simple machine components
(W output / W input) x 100% or (MA / IMA) x 100%
Types of simple machines
pulley - lever - wedge - incline plane - screw

Collision Types

Inelastic collision
the kinetic energy after the collision is less than it originally was
elastic collision
the kinetic energy remains the same after the collision
super elastic collision
the kinetic energy increases after the collision
kinetic energy decreases when the objects stick together


the transl­ation of energy in mechanical ways
Work Formula
Work Unit
Location on graph
under the force - displa­cement curve
Work done by Friction
-fk x d
Work done by Gravity
Work = 0
when the force is perpen­dicular to the displa­cement (90 degrees)
W is positive
if the work is done on the system
W is negative
if the work is done by the system

Mechanical Energy

mechanical energy
the sum of the potential and kinetic energies


P = W/t
Power Unit
Watt = kg.m2/s3


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