P1 - 1.3 Kinetic Energy Flashcards
What is kinetic energy
Energy that an object possesses due to its motion
True or False:
A plane has kinetic energy
True
True or False:
A particle has kinetic energy
True
True or False:
A standstill object has kinetic energy
False
True or False:
A moving object has kinetic energy
True
What 2 things depend on how much energy an object has
Speed
Mass
If we have a mast moving object how does it affect the kinetic energy
It will have more kinetic energy
How does mass affect how much kinetic energy do we have
More mass will mean there is more kinetic energy (as long as speed is the same)
Both objects are moving at 900m/s What has more kinetic energy:
- a plane weighing 20 tonnes
- a particle weighing 0.1g
A plane weighing 20 tonnes will have more kinetic energy
What equation do we use to calculate kinetic energy
Kinetic energy = 1/2 x mass x velocity^2
What is this symbol for: v
Velocity
What does this symbol stand for: m
Mass
What does this symbol stand for: Ek
Kinetic energy
What is mass measured in in kinetic energy calculations
Kilograms
What is kinetic energy measured in
Joules
What is velocity measured in in kinetic energy
Metres per second
m/s
What should you do before starting an equation
Check everything is in the same measurements (etc changing grams to to kilograms)
How many tonnes are in a kilogram
1000
Which has more kinetic energy:
Particle with a speed of 4000m/s and weight of 0.1g or a plane with a speed of 5m/s and a weight of 20 tonnes
Ek = 1/2x(m)x(v^2)
1) convert all the measurements
Particle: 0.1g —> kg
0.1/1000 =0.0001
Plane: 20tonnes —> kg
20x1000=20,000
2) put values into equation
Plane: (0.5 x 20,000)x5^2=250,000J
Particle: (0.5 x 0.0001)x4000^2=800J
3) double check you have answered the question: it is asking which has more kinetic energy
= the plane has more kinetic energy
An object has a mass of 2 kg, and is travelling at a velocity of 5 m/s.
How much kinetic energy does the object have?
Ek=1/2x(m)x(v^2)
Ek= (0.5x2)x5^2=25
Ek= 25J
A cyclist is riding down a hill at a speed of 10 m/s.
The cyclist has 4 kJ of kinetic energy.
Calculate the cyclist’s mass.
Ek=1/2x(m)x(v^2)
1) rearrange the question
m= Ek/0.5xv^2
2) convert the units
4kJ —> J = 4x1000=4,000J
4000/0.5x(10^2)=80kg
How would you rearrange the kinetic energy calculation to find mass
Mass= kinetic energy/ 0.5 x velocity^2
How would you rearrange the kinetic energy calculation to find velocity
Velocity = square root( kinetic energy/ 0.5 x mass)
