Work and Energy Test

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Work and Energy Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

Work done by centripetal force is

A
one

B
less than 0

C
Zero

D
greater than 0

Solution

When a body moves on a circular path. The force that acts on the revolving body towards the center is called centripetal force. As the force acts as right angle to the direction of motion, so work done is 0.

W = FSCosθ

Here , force and displacement are perpendicular to each other, so θ = 90° So, cos90° = 0
∴ W=0 J.
Question 2
1 / -0

For what value of θ is work done maximum?

A
0⁰

B
60⁰

C
45⁰

D
90⁰

Solution

Work done when a body moves at an angle to the direction of force is W= F x S cos θ.
W= F x S cos θ ( cos 0⁰ = 1); So, w = F x S means maximum work is done.
Question 3
1 / -0

1k w h =?

A
3.6 × 10⁶ J

B
3.06 × 10⁴J

C
4.2J

D
36 × 10⁶J

Solution

1 kWh = 1 kW x 1 h

Or, 1kWh = 1000 joule x 3600 s

Or, 1 kWh = 3600000 joule

Or, 1kWh = 3.6 x 10⁶ joule
Question 4
1 / -0

1 W. S = ________?

A
1 joule

B
2 joule

C
10 joule

D
3.6 × 10⁶ joule

Solution

1 Watt = 1 Joule per second and a 1 Joule = 1 Watt times one second.
Question 5
1 / -0

A certain household has consumed 250 units of energy during a month. How much energy is this in joules?

A
10 × 10⁵Joule

B
9 ×10⁸J

C
9 ×10⁶J

D
5 × 10⁸ Joule

Solution

1 unit (Kw-H) = 3.6 × 10⁶ joule
Therefore, 250 units = 250 ×3.6 × 10⁶ joule
= 900 × 10⁶ Joule.
= 9 × 10⁸ Joule.
Question 6
1 / -0

1 meV (mega electron volt) is equal to

A
1.6 ×10¹⁹J

B
1.6 ×10⁻¹⁹J

C
1.6 × 10¹³J

D
1.6×10⁻¹³J

Solution

Electron volt is an unit of energy. One electron volt is equal to 1.6×10⁻¹⁹ joule.

One mega electron = 1.6 × 10⁻¹⁹joule × 1000000 = 1.6 × 10⁻¹³ joules.
Question 7
1 / -0

9800 joule of energy was spent to raise a mass of 50kg, the mass was raised to a height of (take g = 9.8 m/s²)

A
20m

B
10m

C
80 m

D
980m

Solution

P.E = 9800 j. mass = 50kg, g= 9.8 m/s²
Potential energy = mgh,
9800= 50 × 9.8 × h
9800 = 490 × h
h = 9800 / 490 = 20m.
Question 8
1 / -0

A machine does 2000 joule of work in 400 seconds. What is the power of machine?

A
6w

B
5w

C
20w

D
0.5w

Solution

Power =workdone /time
work done = 2000 joule, time = 400 s.
power = 2000 / 400= 5 j/s or 5w.
Question 9
1 / -0

Calculate the time taken by a 150 w bulb of consuming 3000 joule of energy.

A
40 s

B
25 s

C
30 s

D
20s

Solution

Power of bulb = 150w, work done = 3000 joule,
Time taken= work done / power = 3000 / 150 = 20 s.

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Work and Energy Test - 5

Result

Work and Energy Test - 5

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SHARING IS CARING

Question 1

one

less than 0

Zero

greater than 0

Solution

Question 2

00

600

450

900

Solution

Question 3

3.6 × 106 J

3.06 × 104J

4.2J

36 × 106J

Solution

Question 4

1 joule

2 joule

10 joule

3.6 × 106 joule

Solution

Question 5

10 × 105Joule

9 ×108J

9 ×106J

5 × 108 Joule

Solution

Question 6

1.6 ×1019J

1.6 ×10−19J

1.6 × 1013J

1.6×10−13J

Solution

Question 7

20m

10m

80 m

980m

Solution

Question 8

6w

5w

20w

0.5w

Solution

Question 9

40 s

25 s

30 s

20s

Solution

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0⁰

60⁰

45⁰

90⁰

3.6 × 10⁶ J

3.06 × 10⁴J

36 × 10⁶J

3.6 × 10⁶ joule

10 × 10⁵Joule

9 ×10⁸J

9 ×10⁶J

5 × 10⁸ Joule

1.6 ×10¹⁹J

1.6 ×10⁻¹⁹J

1.6 × 10¹³J

1.6×10⁻¹³J