Chapter 6 ~ Work, Energy And Power ⛮ Flashcards
Definition, formula and key 🗝 ideas 💡
Definition of work done :
Plus formula
°the product of the force and the distance moved in the direction of the force
W= F × s
Work done =
Energy ⛮ transferred
1 joule =
1 Newton × 1 m
Therefore, 1 J = 1 Nm
The formula for work done by a gas is
W = p🔼V
W-work done by a gas
p-pressure (remains constant)
🔼V- change in volume
How to derive the work done by a gas formula in 2 steps?
W= p🔼V
Step 1 : F = pressure × area
F = p× A
Step 2 : work done =F × s
Therefore, W = p × A × s
W= p 🔼 V
Definition of gravitational potential energy ⛮
And its formula
°the energy a body has due to its position in a gravitational field
Ep= mgh
m-mass, kg
g- gravitational force, 9.81ms^-2
h- height, m
Definition of gravitational potential
The gravitational potential energy per unit mass at a point in a gravitational field
Definition of gravitational field
°a region where any object with mass experiences a force
Gravitational field strength 💪 plus formula
°The gravitational force experienced by an object per unit mass :
g= F/m
F-force
m-mass
Formula for kinetic energy ⛮
Kinetic energy = 1/2 × mass × speed ^2
KE =0.5×m×v^2
Definition of kinetic energy :
°energy of an object due to its motion
How to derive the formula for kinetic energy in 4 steps
KE =(1/2) mv^2
Step 1 :
Imagine a body being accelerated from rest
The equation of motion v^2 = u^2 +2as
U = 0 (rest)
So v^2 = 2as
Step 2 :
Multiple each side by (1/2)m
So (1/2) mv^2 = mas
Step 3 :
ma = F
So mas is the force × distance moved
Step 4:
Work done by force F= (1/2)mv^2
Decrease in g.p.e =
Gain in k.e.
Decrease in g.p.e =
Gain in k.e.
How to derive g.p.e in 2 steps
Step 1 :
Work done = F × s
Step 2 :
F = W= mg
s = displacement which changes so h
Therefore,
g.p.e = mgh
Formula for efficiency =
Effiency =
(useful output energy /total input energy) × 100
The principle of the conservative of energy is:
Energy ⛮ cannot be created or destroyed. It can only be converted from one form to another.
Definition of power :
➕ Unit
The rate at which energy is transferred or the rate at which work is done.
Unit : Watt (W)
Formula for power =
P = W/t
P- power
W-work done
t-time ⌚
A watt is defined as
A rate of transfer of energy of one joule per second.
The formula for moving power =
P=Force ×velocity
How to derive the formula for moving power (P=F×v) in 3 steps :
Step 1 : W= F× s And distance (s) = v × t
Therefore, W= F × v × t
Step 2 :
P = work done ÷ time ⌚ so,
(F× v × t) /t
Step 3 :
Therefore, P= F × v
