Energy and Power Test

Result

Energy and Power Test - 1

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Weekly Quiz Competition

Question 1
1 / -0

Use the following information to answer the next question.

A man lifts an LPG cylinder of mass 16 kg to load on a truck of height 1.2 m.

What is the work done by the man to load 55 such cylinders?

A
130.67 J

B
188.16 J

C
7186.8 J

D
10348.8 J

Solution

Mass of an LPG cylinder, m = 16 kg

Height of the stage of a truck, h = 1.2 m

Acceleration due to gravity, g = 9.8 m/s²

Work done by the man on one LPG cylinder is given by the relation,

W = mgh = 16 × 9.8 × 1.2 = 188.16 J

Therefore, the net work done by the man in order to load 55 LPG cylinders is 55 × 188.16 i.e., 10348.8 J.
Question 2
1 / -0

Use the following information to answer the next question.

A body of mass 12 kg is placed on a hypothetical ice pole of length 5.4 m. The temperature around the pole is such that ice melts 1 cm every second.

What is the energy possessed by the body after 3 minutes?

A
392.02 J

B
423.36 J

C
524.12 J

D
635.04 J

Solution

Mass of a body, m = 12 kg

Height of the body from the ground = Length of the ice pole, h = 5.4 m

Acceleration due to gravity, g = 9.8 m/s²

Length of the pole reduces by 1 cm in 1 s. Total length reduced by the ice pole in 3 minutes, i.e. in 180 s, will be 180 × 1 = 180 cm = 1.8 m

Hence, new height of the body after 3 minutes, h’ = 5.4 − 1.8 = 3.6 m

Potential energy possessed by the body is given as

P = mgh' = 12 x 9.8 x 3.6 = 423.36 J

Therefore, after 3 minutes, the potential energy possessed by the body is 423.36 J.
Question 3
1 / -0

One solar cell can provide 100 Watt hours of electrical energy. The given table lists the power consumed by different appliances and the time for which each is used daily

Appliance Power (in watts) Time (in hours)

Bulb 60 14

Fan 40 12

Fridge 1,000 24

George has five bulbs, two fans, and one fridge. He wishes to run these appliances using solar cells.
The numbers of solar cells required for this purpose are

A
292

B
320

C
425

D
540

Solution

The total electrical energy required by the appliances is

(5 × 60 W × 14 h) + (2 × 40 W × 12 h) + (1,000 × 24 h) = 29,160 Wh

One solar cell can provide 100 Wh of electrical energy.
Therefore, the total number of solar cells required are 29160/100 = 291.6

The number of solar cells can only be in whole numbers. Hence, the number of cells required are 292.