Energy Flashcards
State the nine different forms of energy
Kinetic (Ke) - movement energy
Gravitational Potential Energy (gpe) - when an object is lifted
Elastic Potential Energy (epe) - when an object is stretched or compressed
Chemical - stored in chemical bonds (fuels like food)
Heat (thermal) - often wasted energy
Sound - often wasted energy
Light - often wasted energy
Electrical
Nuclear- stored in nuclear bonds and released in atomic bombs/nuclear power stations (from the nucleus of an atom)
What is an easy way of remebring the nine forms of energy?
Every (elastic)
Kid (kinetic)
Loves (light)
Not (nuclear)
Hates (heat)
G (gravitational)
C (chemical)
S (sound)
E (elastic)
State the law of the conservation of energy
‘Energy cannot be created or detroyed but can be converted from one form into another.’
Can the amount of energy in the universe change? Why?
no because of the principle of the conservation of energy (it cannot be created or destroyed so there cannot be more or less)
What is energy?
energy is the ability to do work on objects and it converts from one form to another
What is work?
work is done when force is applied to an object and the object is moved through a distance
What is the equation for work?
work = force x distance moved in the direction of the force
measurements - Joules (J) = Newtons (N) x Metres (m)
w= f x d
What is the equation for GPE?
GPE= mass x gravity x height
measurments- Joules (J) = kg x N/kg x m
gpe = mgh
What is the equation for kinetic energy?
kinetic energy= 1/2 x mass x velocity2
measuremnts - Joules (J) = kg x v in m/s
Ek = 1/2 mv2 (notice only v is squared)
What is power?
power is the rate of doing work
rate means per time/per unit time
What is the equation for power?
power = work ÷ time
p= w÷t
What is power measured in?
power is measured in Watts
1W= 1 J/s
1KW = 1000W
1MW = 1000,000 W
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Calculate the increase in GPE for the girl in going between G and A floor
GPE= mgh
=65 x 10 x(6 x 1)
=3900 J
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Calculate the total increase in her GPE from G to D floor
GPE= mgh
= 65 x 10 x (6 x 4)
= 15600J
A 65kg girl enters receptipn at A floor.She walks down to G floor and then all the way up to D floor. All the floors are 6m high. Explain why she feels tired
she has done work by walking
she has converted chemical energy into gravitational, kinetic and thermal energy
A 200g mass is lifted 5.0m off the ground. Calculate the work done in lifting it
GPE= mgh
0.2 (remember to convert 200g into kg) x 10 x 5
=10J
A 900kg car is moving at 5 m.s. how much kinetic energy does it have?
Ek= 1/2 mv2
=1/2 x 900 x (5)2
=450x25
=11250 J
A 90kg runner is moving at a constant velocity of 12 m/s. Calculate the kinetic energy
Ek= 1/2 x 90 x (12)2
=6480J
A 1000kg car is travelling at 15m/s on the motorway. Calculate the work done (change in energy) when it accelerates to 18 m/s
Ek= 1/2 x 1000 x (182-152) [You have to take the original velocity away from the new velocity]
= 49500J
Rearrange the kinetic energy equation so that velocity is the subject
Ek=1/2 x m x v2
Ek x 2 = m x v2
Ek x 2 ÷ m = v2
v2 = 2Ek/m
v = √ 2Ek/m
A 700kg car has 12000J of kinetic energy. Calculate its velocity
v = √ 2Ek/m
v = √ 2x12000/700
=5.86 m/s (2.dp)
What is the efficiency and its equation?
how much useful energy is produced from the total energy put into the machine
effeciency = total useful output/total input x 100
What is a sankey diagram?
it shows how well a machine uses energy
shows efficiency or inefficiency of something
How do you draw a Sankey Diagram?
the thicker the arrow, the more energy it represents
useful energy is shown going left or right
wasted energy is shown going upwards or downwards
the length of the arrows doesn’t matter
if on graph paper or specified, every square and placing matters (the starting of the output and the calculations of the thickness of the arrow)











