Lesson 5, Topic 4
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# Calculations Involving Workdone

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Examples:

1. A boy of mass 20kg climbs stairs of about 8m. Calculate the work done by the body. The face of gravity acting on a mass = 10m/s2

Solution:

Workdone = mgh

Where m = mass of the body; g = force of gravity; h = distance.

.: W = 20 x 10 x 8

= 1600J

2. A boy of mass 10 kg runs up a set of steps of total height 3.00m. find the work done against gravity.

Solution:

W = mgh

= 10 x 10 x 3

= 300J

Evaluation Questions on Work, Energy, and Power:

1. Define the following terms:

i. Work

ii. Energy

iii. Power.

2. List seven forms of energy

3. State the SI unit of work, energy, and power.

4. Calculate the work done if a body exerts a force of 10N over a distance of 50m.

5. Outline 5 different forms of energy.

6. Calculate the kinetic energy of a car of mass 40kg when accelerating at a velocity 30 m/s.

7. Name the energy changes in each example given below:

i. a torchlight

ii. a Bunsen burner

iii. a loud speaker

iv. electric bell

v. a dynamo.

Reading assignment: spectrum basic science for junior secondary schools, book 2 pages 101 – 106. error: