Question

1) Anna uses a force of 20N to push a lawnmower 4m. in 1s. if the garden is 60m long, then what is her power?
a) 600 W
b) 1000 W
c) 1200 W
d) 2000 W

2) Which material is used for the electromagnet in a magnetic relay?
a) Steel
b) Soft iron
c) Alloy
d) Cobalt

3) A man streaches a rubber band 20 times in 1 min doing 20j of work each time. what is his power?
a) 2W
b) 3W
c) 7W
d) 9W

4) A motor has a useful power output of 3KW. How much useful work does it do in 1s?
a) 3000j
b) 2000j
c) 4000j
d) 3500j

5) If an engine does 800j work in 4s, which is its useful power output in W?
a) 400 W
b) 300 W
c) 500 W
d) 200 W

6) A stone of 1kg hits the ground at a velocity of 40 m/s. what is the height from where it is dropped?
a) 40 meters
b) 80 meters
c) 60 meters
d) 50 meters

7) A brick of mass 2kg is lifted of 180 meters above the ground and then dropped. what is the kinetic energy of the brick just before it hits the ground?
a) 50m/s
b) 30m/s
c) 40m/s
d) 60m/s​

Answer 1

Explanation:

work done is given by F.S

Dot product of force and displacement which means W=∣F∣.∣S∣Cosθ

means W=20×1×Cos45

W=10

2

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