energy

Question 1

Name the 8 energy stores

Answer 1

Thermal
Kinetic
Gravitational Potential
Elastic Potential
Chemical 
Magnetic
Electrostatic
Nuclear

Question 2

How can energy be transferred?

Answer 2

Mechanically (by a force doing work)
Electrically (work done by moving charges)
Heating
Radiation (e.g. light or sound)

Question 3

What is a closed system?

Answer 3

Where matter and energy cannot enter or leave.

Question 4

Explain energy in a moving object:

Answer 4

Everything that moves has a kinetic energy store.

It speeds up when more energy is transferred in and slows when there is a transfer out.

Question 5

Equation for kinetic energy:

Answer 5

Ek = ½ MV²
Kinetic energy (Joules,J) = 1/2 x mass (kg) x speed² (m/s)²

Question 6

Equation for gravitational potential energy

Answer 6

Ep = mgh

Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)

Question 7

Describe raised objects in terms of gravitational potential energy.

Answer 7

Lifting object in grav field requires work.
Transfer of energy to g.p.e.s.
Higher the object lifted, more energy transferred.
See equation.

Question 8

What happens with falling objects?

Answer 8

As g.p.e.s decreases, k.e.s increases.

Question 9

what is the equation for change in thermal energy

Answer 9

change in thermal energy = mass(Kg) x specific heat capacity x change in temperature

Question 10

what is the equation for power?

Answer 10

power(W) =energy transferred(J)/time(s)

P = E/t

Question 11

what is another equation for power?

Answer 11

Power(W) = work done(J)/ time(s)
P = W/t

Question 12

what’s an equation for efficiency?

Answer 12

efficiency = useful output energy transfer/total input energy transfer

Question 13

what’s an equation for efficiency?

Answer 13

efficiency = useful power output/total power input