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#### Force and Motion Book Back Questions

7th Standard EM

Reg.No. :
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Science

Time : 00:45:00 Hrs
Total Marks : 30
3 x 1 = 3
1. A particle is moving in a circular path of radius r. The displacement after half a circle would be

(a)

Zero

(b)

R

(c)

2 r

(d)

r / 2

2. Suppose a boy is enjoying a ride on a marry go round which is moving with a constant speed of 10 m/s. It implies that the boy

(a)

at rest

(b)

moving with no acceleration

(c)

in accelerated motion

(d)

moving with uniform velocity

3. What is one way you might increase the stability of an object?

(a)

lower the centre of gravity

(b)

raise the centre of gravity

(c)

increase the height of the object

(d)

shorten the base of the object

4. 3 x 1 = 3
5. If the velocity of an object increases with respect to time, then the object is said to be in__________ acceleration.

()

positive

6. The slope of the speed–time graph gives _____

()

velocity

7. In ___________ equilibrium its centre of gravity remains at the same height when it is displaced.

()

neutral

8. 4 x 1 = 4
9. Displacement

10. (1)

Uniform velocity

11. Light travels through vacuum

12. (2)

Knot

13. Speed of ship

14. (3)

Metre

15. Centre of gravity of the geometrical shaped object

16. (4)

Geometric centre

1 x 5 = 5
17. A car started from rest and travelling with velocity of 20 m /s in 10 s. What is its acceleration?

18. 2 x 2 = 4
19. All objects having uniform speed need not have uniform velocity. Describe with the help of examples.

20. Correct your friend who says “The acceleration gives the idea of how fast the position changes”.

21. 2 x 3 = 6
22. Show the shape of the distance – time graph for the motion in the following cases.
a. A bus moving with a constant speed.
b. A car parked on a road side.

23. What is centre of gravity ?

24. 1 x 5 = 5
25. Explain the types of stability with suitable examples.