UNIT 1 - Energy Concepts

Question 1

Define work and the equation for it

Answer 1

The product of force and distance moved in the direction of the force when the force is constant

Work done = Force x cos(angle) x distance

W=Fcos(angle)X

(Joules)

Equation becomes w=fx if there is no angle or angle is 0

Question 2

Define energy

Answer 2

Ability to do work (Joules)

Question 3

Is energy and work scalar or vector

Answer 3

Both scalar

Question 4

What is the principle of conservation of energy

Answer 4

Energy cannot be created or destroyed, only transferred from one form to another. Energy is a scalar

Question 5

Equation for kinetic energy

Answer 5

E = 1/2mv²

Kinetic energy(J) = 1/2 x mass(kg) x speed²(ms⁻¹)

Question 6

What is gravitational potential energy

Answer 6

The energy possessed by an object due to its position or height above the earth

Question 7

How to derive equation for gravitational

Answer 7

W = fx
F= ma (a = g, gravitational field strength)

W = mgx
Distance = height

gpe = mgh
Gravitational potential energy = mass x gravitational field strength x height

Question 8

Define kinetic energy

Answer 8

Energy possessed by a moving object

Question 9

Define elastic potential energy

Answer 9

Potential energy stored as
a result of deformation of an elastic object.
(Such as the stretching of a spring)

Question 10

Equations for elastic potential energy?

Answer 10

PE = 1/2kx²
or
Pe = 1/2Fx

Question 11

Equation for spring constant

Answer 11

K = f/x

Question 12

Explain how KE and GPE changes at points when a ball is thrown into the air

Answer 12

As its thrown into the air KE decreased and GPE increases, KE>GPE

At some point it then stops, KE has decreased to zero and GPE has reached maximum

It then starts to fall back down, as it falls back down KE increases, GPE decreases
KE<GPE

Question 13

How to work out energy lost due to friction?

Answer 13

KE = GPE + heat + sound
GPE = KE + heat + sound

Question 14

How to work out force or distance of the energy lost due to friction?

Answer 14

Heat + sound = work done

Question 15

What is power and units

Answer 15

The rate of doing work

Watts(W) or Js⁻¹

Question 16

Equation for power (thats not
Given)

Answer 16

P = Fv
Power = force x velocity

Question 17

Equation for efficiency thats not given

Answer 17

% efficiency = useful power output/total power output x 100%

Question 18

How can efficiency be represented in diagrams

Answer 18

By a sankey diagram
Which are schematic representations of energy transfers in which the width of the arrows used shows the percentage of the total input energy form

Question 19

What are the 9 types of energy

Answer 19

Kinetic
Gravitational potential
Elastic potential
Chemical
Electrical
Radiant
Internal
Thermal/heat
Sound

Question 20

Define chemical energy

Answer 20

Energy stored in mixtures of chemicals or chemical compounds (coil, oil, gas)

Question 21

Define electrical energy

Answer 21

Energy transferred in electrical circuits by the motion of charge carriers such as electrons

Question 22

Define radiant energy

Answer 22

The energy carried by all types of electromagnetic waves (xrays, uv, infa-red, etc)

Question 23

Define internal energy

Answer 23

Energy possessed by a body due to the random distribution of the kinetic and potential energies of the molecules which make it up

Question 24

Define thermal energy

Answer 24

Energy due to the temperature of an object

Question 25

Define sound energy

Answer 25

Energy produced by vibrating objects