P1 - Conservation And Dissipation Of Energy

Question 1

What are the energy stores?

Answer 1

Chemical energy
Kinetic energy
Gravitational potential energy
Elastic potential energy
Thermal energy

Question 2

How can energy be transferred?

Answer 2

Heating
Waves
Electric current
Force moves an object

Question 3

What is a flow diagram?

Answer 3

Shows the energy transfer

Question 4

When an object falls how do energy stores change?

Answer 4

Gravitational potential energy
To
Kinetic energy
To
Thermal energy

Question 5

When a pendulum swings how do energy stores change?

Answer 5

Maximum gravitational potential energy at far left and right and maximum kinetic energy at the bottom in the middle.

Question 6

What is a system?

Answer 6

An object or a group of objects

Question 7

Wyatcisvtye conservation of energy?

Answer 7

Energy cannot be created or destroyed, only transferred

Question 8

What energy transferred happen to a bungee jumper after jumping of a platform?

Answer 8

Rope is slack energy is gravitational potential
Kinetic energy when they jump due to gravity
Role tightens and kinetic energy decreases and elastic potential energy increases.
Rope recoils and elastic potential decreases and kinetic store increases.
Some energy throughout is transferred to thermal store of surroundings by heating.

Question 9

What is work?

Answer 9

When an object is moved by a force work is done on the object by the force so the force transfers energy to the object.

Question 10

What is the equation for energy transferred?

Answer 10

Energy transferred = work done

Question 11

How do you calculate the work done by a force when it causes displacement of an object?

Answer 11

Work done = force applied * distance moved
Joules = newtons * metres

Question 12

How do you overcome friction?

Answer 12

Transferred to thermal energy stores by heating if you rub your hands together.

Question 13

What is the force needed ti life an object at a constant velocity equal and opposite to?

Answer 13

Gravitational force on the object.

Question 14

When does gravitational potential energy increase and decrease?

Answer 14

When an object is lifted y, gravitational potential energy increases. When the object is lowered down, energy decreases.

Question 15

What is the equation for change in object’s gravitational potential energy store?

Answer 15

Change in gravitational potential energy store = weight * change of height

Joules = newtons * metres

Question 16

What is another equation for change of gravitational potential energy store?

Answer 16

Change of gravitational potential energy store = mass * gravitational field strength * change of height
Joules = kilograms * N/kg * metres

Question 17

What do results show about kinetic energy?

Answer 17

The greater the height dropped from, the faster the speed.

Question 18

What happens to kinetic energy if speed increases?

Answer 18

Increases

Question 19

What is speed dropped compared to kinetic energy?

Answer 19

Kinetic energy is directly proportional to the square of its speed

Question 20

What store is used when you stretch something?

Answer 20

Elastic potential energy.

Question 21

How do you calculate kinetic energy?

Answer 21

Kinetic energy = 1/2 * mass * speed squared

Joules = 1/2 * kg * m/s squared

Question 22

How do you calculate elastic potential energy?

Answer 22

Elastic potential energy = 1/2 * spring constant * extension squared

Joules = 1/2 * N/m * meters squared

Question 23

What is useful energy?

Answer 23

Energy transferred to where it is wanted in the way that is wanted

Question 24

What is wasted energy?

Answer 24

The energy that is not usefully transferred.

Question 25

What happens when energy is not transferred usefully?

Answer 25

It is dissipated and stored in less useful ways .

Question 26

What happens with energy stores when you exercise?

Answer 26

As you exercise, energy is transferred by your muscles to the thermal energy store.

Question 27

What happens to wasted energy?

Answer 27

It is dissipated to the surroundings

Question 28

What happens the more energy spreads out?

Answer 28

It becomes less useful.

Question 29

What is weight measured in?

Answer 29

Newtons.

Question 30

What is energy measured in?

Answer 30

Joules

Question 31

What is the input energy?

Answer 31

Energy supplied to a device .

Question 32

What is useful output energy?

Answer 32

Useful energy transferred by the device

Question 33

What is the rule of conservation of energy?

Answer 33

Energy cannot be created or destroyed only transferred.

Question 34

What is the equation for input energy?

Answer 34

Useful output energy + energy wasted

Question 35

What is the equation for efficiency?

Answer 35

Useful output energy transferred by the device / total input energy supplied to the device.

Question 36

What do devices waste energy?

Answer 36

Friction between the moving parts causes heating The resistance of a wire causes it to get hot when a current passes through. Air resistance causes a force on a moving object that opposes its motion. Energy transferred from the object to the surroundings by this force is wasted. Sound created by machinery causes energy transfer to the surroundings.

Question 37

How do you reduce energy loss?

Answer 37

Lubricate the moving parts to reduce frictions In circuits, use wires with as little electrical resistance as possible. Streamline the shapes of moving objects to reduce air resistance. Cut out noise bi tightening loose parts to reduce vibration

Question 38

What is the useful energy and energy wasted in a light bulb?

Answer 38

Useful = light emitted from the glowing filament Wasted = energy transferred from the filament heating the surroundings

Question 39

What is the useful energy and energy wasted in an electric heater?

Answer 39

Useful = energy heating the surroundings Wasted = light emitted from the glowing element.

Question 40

What is the useful energy and energy wasted in an electric toaster?

Answer 40

Useful = energy heating bread Wasted = energy heating the toaster case and the air around it

Question 41

What is the useful energy and energy wasted in an electric kettle?

Answer 41

Useful = energy heating water Wasted = energy heating the kettle itself

Question 42

What is the useful energy and energy wasted in a hairdryer?

Answer 42

Useful = kinetic energy of the air driven by the fan, energy heating air flowing past the heater filament. Wasted = sound of fan motor, energy heating The hairdryer itself

Question 43

What is the useful energy and energy wasted in an electric motor?

Answer 43

Useful = kinetic energy of objects driven by the motor, gravitational potential energy of the objects lifted by the motor. Wasted = energy heated by the motor and energy transferred by the sound waves generated by the motor.

Question 44

What is power?

Answer 44

The energy you supply per second

Question 45

How does power affect energy?

Answer 45

The more powerful an appliance is, the faster the rate at which it transfers energy.

Question 46

What is power measured in?

Answer 46

Watts or kilowatts

Question 47

What is the equation for power?

Answer 47

Power = energy transferred to the appliance / time taken for energy to be transferred. Watts = joules / seconds

Question 48

What is the equation for power wasted?

Answer 48

Power wasted = total power in - useful power out

Question 49

What is the equation for efficiency?

Answer 49

Efficiency = useful power out / Toya power in all * 100