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AS- Level Wjec Physics > Unit 1.4 Energy concepts > Flashcards

Unit 1.4 Energy concepts Flashcards

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1
Q

Define work.

A

It is done when a force moves its point of application.

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2
Q

Define energy.

A

The energy of a body or system is the amount of work it can do.

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3
Q

Give the units for work.

A

Joule (J)

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4
Q

What type of quantity is energy?

A

Scalar quantity

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5
Q

What is kinetic energy?

A

Energy due to motion.

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6
Q

State the formula work done.

A

Work done = Force x Distance moved in the direction of the force

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7
Q

State the formula for work done in symbols.

A

W = Fx

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8
Q

Give the units for the symbol “W”, in work done formula.

A

(J) - Joules

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9
Q

Give the units for the symbol “F”, in work done formula.

A

(N) - Newtons

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10
Q

Give the units for the symbol “x”, in work done formula.

A

(m) - metres

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11
Q

State another way of saying work done.

A

Energy transfer

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12
Q

Explain energy.

A

Quantity of energy transferred is equal to the work done by force.

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13
Q

State 2 other formulas for work done.

A

(1) Work done = Force x Component of displacement in the direction of the force

(2) Work done = Component of force in the direction of displacement x Displacement

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14
Q

State the 2nd formula of work done in symbols.

A

W = Fxcosθ

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15
Q

Explain in terms of energy, if θ = 90°

A

No work is done; no energy is transferred.

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16
Q

Explain in terms of energy, if θ > 90°

A

The work is negative and energy is transferred from the object.

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17
Q

State the principle of conservation of energy.

A

The total energy of an isolated system is constant though it can be transferred within the system.

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18
Q

State the principle of conservation of energy in symbols.

A

ΔE - FvΔt - FvΔt = 0

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19
Q

What does the principle of conservation of energy mean?

A

Work done = energy transfer

20
Q

Define kinetic energy (KE or Eₖ).

A

The energy possessed by a body by virtue of its motion.

21
Q

State the formula for KE.

A

KE = 1/2 mv²

22
Q

Explain the formula for KE.

A

It is the KE of a body of mass “m” travelling with velocity “v”.

23
Q

Define gravitational potential energy (GPE or PE or Eₚ).

A

The energy possessed by an object by virtue of its position.

24
Q

State the formula for GPE.

A

ΔEₚ = mgΔh

25
Q

Define elastic potential energy (Eₚ).

A

The energy stored in a body by virtue of its deformation.

26
Q

Give examples of elastic objects.

A
  1. Rubber bands
  2. Springs
  3. Rulers
27
Q

Describe elastic objects.

A

Elastic objects which are deformed are able to do work on other objects when they return to their normal shape.

28
Q

Give 3 ways for an object to be deformed.

A
  1. Stretched
  2. Compressed
  3. Bent
29
Q

What does the extent of deformation depend upon?

A

The applied force

30
Q

State the formula for Hooke’s law.

A

F = kx

31
Q

Define “k” in the formula for Hooke’s law.

A

Spring constant, k

32
Q

Define “F” in the formula for Hooke’s law.

A

Applied force, F

33
Q

Define “x” in the formula for Hooke’s law.

A

The deformation (e.g. stretch), x

34
Q

State the formula for elastic potential (Eₚ).

A

Eₚ = 1/2 kx²

35
Q

Define power.

A

The work done per unit time or the energy transferred per unit time.

36
Q

Give the SI units and the normal units for power.

A

(W) - watt
SI Units - J s⁻¹

37
Q

State the formula for power.

A

Power = energy transferred/ time

38
Q

State the formula for power in symbols.

A

P = E / t

39
Q

State the formula for energy transferred.

A

Energy = Power x time

40
Q

State the 2nd formula for power.

A

Power = work done / time

41
Q

State the 2nd formula for power in symbols.

A

P = W / t

42
Q

State the 3rd formula for power.

A

P = Fvcosθ

43
Q

What is the increase in GPE equal to?

A

The work done against the force of gravity.

44
Q

What is the increase in EPE equal to?

A

The work done against the tension within the object when we stretch it.

45
Q

Define efficiency.

A

It is the fraction of the energy input which is transferred usefully by the system.

46
Q

Define efficiency as a formula.

A

Efficiency = ( useful energy transfer / total energy input ) x 100%

AS- Level Wjec Physics (5 decks)

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