P1 Flashcards
Different types of energy stores: (8)
- Thermal
- Kinetic
- Magnetic
- Chemical
- Gravitational potential
- Elastic potential
- Nuclear
- Electrostatic
What is a system
An object or group of objects
Why does cycling uphill affect the maximum speed of a cyclist?
The maximum speed is lower. The maximum power output of the cyclist is constant but additional work is done against gravity
How can energy be transferred?
heating, waves, electrical current, a force when in moves an object
What is a closed system?
A system in which no energy transfers take place out of or into the energy stores of the system
Describe the motion of a pendulum
As it moves towards the middle, energy is transferred by the force of gravity from its gravitational potential energy store to its kinetic energy store. So its gravitational energy store decreases and its kinetic energy store increases.
As it moves away from the middle, its kinetic energy store decreases and its gravitational potential energy store increases. If the air resistance on the bob is very small the bob will reach the same height each side.
What energy transfers happen to a bungee jumper after jumping off a platform?
When the rope is slack, energy is transferred from the gravitational potential energy store to the kinetic energy store as the jumper accelerates towards the ground due to the force of gravity.
When the rope tightens, it slows the bungee jumper’s fall. This is because the force of the rope reduces the speed of the jumper. The jumper’s kinetic energy store decreases and the rope’s elastic potential energy store increases as the rope stretches. Eventually, the jumper comes to a stop as the energy that was originally in the kinetic energy store of the jumper has all been transferred into the elastic potential energy store of the rope.
After reaching the bottom, the rope recoils and pulls the jumper back up. As the jumper rises, the energy in the elastic potential energy store of the rope decreases and the bungee jumper’s kinetic energy store increases until the rope becomes slack, and at the top of the ascent the bungee jumper’s kinetic energy store decreases to zero. Their gravitational potential energy store increases throughout the ascent.
The bungee jumper doesn’t return to their original height as some energy is transferred to the thermal energy store of the environment as the rope is stretched and shortened.
Equation for work done
work done (J) = force applied (N) x distance moved along the line of action of the force (m)
Where is the work done to overcome friction transferred to?
The thermal energy stores of the objects that rub together and the surroundings
Equation for change in an objects gravitational potential energy store
change in an object’s gravitational potential energy store (J) = weight (N) x change of height (m)
equation for change of gravitational potential energy store
change of gravitational potential energy store (J) = mass (Kg) x gravitational field strength (N/Kg) x change of height (m)
Equation for kinetic energy
Kinetic energy (J) = 1/2 x mass (Kg) x Speed2
Describe the practical for investigating how the kinetic energy store of an object depends on its speed
- The ball is placed on a slope from a measured height above the foot of the slope. You can calculate the decrease in its gravitational potential energy by using the equation gpe = mass x gravitational field strength x change in height
- the decrease in gravitational potential energy is matched by an equal increase in its kinetic energy store
- The ball is timed using light gates, over a measured distance between X and Y after the slope
What is useful energy?
energy transferred to where it is wanted in the way that it is wanted
What is wasted energy?
Energy that is not usefully transferred
