Chapter 1.6 Work, energy and power - Summary Edexcel A Level Physics Student Book 1 - Physics (9PH0)

1.6 - Work, energy and power
Energy
● Work is done by a force when the object moves in the direction of force (and the
force therefore transfers energy from one object to another)




○
● ***W ( work done[ J ])=( F( force [N ])×cos θ)× s (distance [m])
○ ***Joule: amount of work done due to a force; 1 J moves an object of 1 N for
1m
● Energy to lift = energy supplied - energy dissipated, ie ***if mass of object is kept
constant, energy used to raise it COMPLETELY vertically remains the same
● ***Gravitational potential energy (GPE): energy transferred when moving an object
of mass m and height h against a gravitational field strength g




○
Ie going up the slope l has same GPE as directly rising a height of h
● ***Kinetic energy (KE): KE stored in a moving object equals the amount of work
done accelerating it from stationary to that speed
1 2
● Δ GPE=mg Δ h, KE= m v
2
○ ∴ Combining 2 equations, *** v=√❑
○ Derivation of KE equation:
■ v2 = u2 + 2as
■ ASSUME object is stationary at the start, u = 0 → v 2 = 2as
v2
■ =as
2
■ ∵ F = ma, W = Fs, ∴ W = mas



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