Objectives
Relate (without calculation)
power to work done and time
taken, using appropriate
examples
Recall and use the equation P =
E/t in simple systems.
Outcomes
C: Describe what power is in relation
to work.
B: Calculate power for various
problems.
A: Carry out multiple step
calculations involving energy, work
and power successfully.
Key terms: work, power, energy, time, watts, joules
Outcomes
C: Describe what
power is in relation
to work.
B: Calculate power
for various problems.
A: Carry out multiple
step calculations
involving energy,
work and power
successfully.
Key terms: work, power, energy, time, watts, joules
Outcomes
C: Describe what
power is in relation
to work.
B: Calculate power
for various problems.
A: Carry out multiple
step calculations
involving energy,
work and power
successfully.
Key terms: work, power, energy, time, watts, joules
Outcomes
C: Describe what
power is in relation
to work.
B: Calculate power
for various problems.
A: Carry out multiple
step calculations
involving energy,
work and power
successfully.
Key terms: work, power, energy, time, watts, joules
Calculating power question 1
A lawnmower engine does 10 kJ
of work in 10 seconds. What is
the power of the engine?
power =
work done
time
= 10,000 / 10
= 1,000 W = 1 kW
Calculating power question 2
A car transfers 12 MJ of energy in
2 minutes. What is the power of
the car?
power =
work done
time
= 12,000,000 / 120
= 100,000 W = 100 kW
=
energy transfer
time
Power, work and time calculations
Task
Outcomes
Calculate the work done and
power of you moving across the
classroom.
C: Describe what power is in relation
to work.
Show all measurements and
calculations carried out.
A: Carry out multiple step
calculations involving energy, work
and power successfully.
B: Calculate power for various
problems.
Key terms: work, power, energy, time, watts, joules
Task
Outcomes
Answer the questions on work,
energy and power
C: Describe what power is in relation
to work.
B: Calculate power for various
problems.
A: Carry out multiple step
calculations involving energy, work
and power successfully.
Key terms: work, power, energy, time, watts, joules
Key terms: work, power, energy, time, watts, joules
Key terms: work, power, energy, time, watts, joules
Key terms: work, power, energy, time, watts, joules
Key terms: work, power, energy, time, watts, joules
Key terms: work, power, energy, time, watts, joules
Extension
1. Anuar runs up a 2.91-meter high flight of stairs at a constant speed in 2.15 seconds. If Anuar’s mass
is 55.9 kg, determine the work which he did and his power rating.
2. On a recent adventure trip, Lucia went rock-climbing. Lucia was able to steadily lift her 45.0-kg body
20.0 meters in 100 seconds. Determine Lucia's power rating during this portion of the
climb.
3. Hina owns a family of squirrels. The squirrels have been trained to do push-ups in
repetitive fashion. Being connected to an electrical generator, their ongoing exercise is used to help
power the home.
There are 23 squirrels in the family and their average mass is 1.1 kg.
They do work on the "up" part of the push-up, raising their body an average distance of 5.0 cm.
If the squirrels averages 71 push-ups per minute, then determine the total amount of work done in
one minute and the power generated by their activity
4. An elevator motor lifts 715 kg of mass to the height of the fourth floor of an office building (11.0
meters above ground level) at a constant speed in 9.35 seconds. Determine the power rating of the