Papper One Physics Flashcards
What are the eight types of energy source
Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
What is a closed system
Where neither matter nor energy can enter or leave and the net change in total energy of a closed system is always zero
What does work done mean
Energy being transferred
What is a system
An object or group of objects
If an apple falls from a tree what is happening to transfer of energy
Energy is transferred from gravitational potential energy to kinetic energy store
What is kinetic energy
Energy store in moving objects
What is the kinetic energy of stationery objects
Zero
A car with a mass of 700kg is moving with a speed of 20 m/s. Calculate the kinetic energy for the car
Kinetic energy = 0.5 x mass x speed^2
Kinetic energy = 0.5 x 700 x 20 = 140,000 J
Kinetic energy = 140 KJ
A cyclist and bike have a total mass of 100Kg and a speed of 15 m/s. Calculate the kinetic energy.
Kinetic energy = 0.5 x m x v^2
Kinetic energy = 0.5 x 100 x 15^2=11250 J
Kinetic energy = 11.25 KJ
A tennis ball is travelling at 50 m/s and has a kinetic energy of 75J. Calculate the mass of the tennis ball.
Kinetic energy = 0.5 x mass x speed^2
Mass = kinetic energy / 0.5 x speed^2
75/0.5 x50^2
Mass = 0.06 kg
What happens when you stretch a spring
We’re applying a force to change the length of the spring
When you put energy into a spring to stretch it the stretch spring is storing this energy and we call that…
Elastic potential energy
What is the relationship between extension(m) and force applied(N)
Directly proportional
What is gravitational potential energy
Energy stored in an object due to it’s position above earth’s surface
A crane lifts a 75kg mass a height of 8m. Calculate the gravitational potential energy gained by the mass. (Gravitational field strength = 9.8 N/kg)
Gravitational potential energy = mass x gravational field strength x height
GPE = 75 x 9.8 x 8 = 5880 J
A ball with a mass of 500g is lifted onto a shelf which is 1.5m above the ground. Calculate the gravitational field strength gained by the ball.
GPE = mass x height x GFS
GPE = 0.5 x 9.8 x 1.5
GPE = 7.35 J
Calculate the energy required to increase the temperature of 2kg of water from 20oc to 100oc. The specific heat capacity for water is 4200 j/kg 0c
Change in thermal energy = mass x specific heat capacity x temperature change
Change in thermal energy = 2 x 4200 x 80 = 67200
=672 kj
An iron has aluminium plate with a mass of 1.5kg. Calculate the thermal energy stored in the plate when the temperature rises from 20oc to 200oc. The specific heat capacity of aluminium is 913 J/kgoc
Change in thermal energy = mass x specific heat capacity x temperature change
Change in thermal energy = 1.5 x 913 x 180 =246510J
Kinetic energy definition
The energy stored in a moving object
Gravitational potential energy definition
The energy stored due to an objects position above the ground.
Elastic potential energy definition
Energy stored in a stretched spring
Thermal energy definition
Energy stored due to an objects temperature
What is the law of conservation of energy
Energy can be transferred usefully, stored or dissipated but it cannot be created or destroyed
How can u reduce unwanted energy transfers
We can reduce unwanted energy transfers by reducing friction.
-use a lubricant e.g. oil on the fixed point
-remove air particles from around the pendulum
When energy is transferred from one store to another…
Work is done