Class 8
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Science
Exploring Forces
NCERT Solutions
NCERT Solutions
Exploring Forces
10 Solutions
Q1
Keep the curiosity alive
Match items in Column A with the items in Column B.
| Column A (Type of force) | Column B (Example) |
| :----------------------- | :---------------------------------------------------------------------- |
| (i) Muscular force | (a) A cricket ball stopping on its own just before touching the boundary line |
| (ii) Magnetic force | (b) A child lifting a school bag |
| (iii) Frictional force | (c) A fruit falling from a tree |
| (iv) Gravitational force | (d) Balloon rubbed on woollen cloth attracting hair strands |
| (v) Electrostatic force | (e) A compass needle pointing North |
Q2
Keep the curiosity alive
State whether the following statements are True or False.
(i)
A force is always required to change the speed of motion of an object.
(ii)
Due to friction, the speed of the ball rolling on a flat ground increases.
(iii)
There is no force between two charged objects placed at a small distance apart.
Q3
Keep the curiosity alive
Two balloons rubbed with a woollen cloth are brought near each other. What would happen and why?
Q4
Keep the curiosity alive
When you drop a coin in a glass of water, it sinks, but when you place a bigger wooden block in water, it floats. Explain.
Q5
Keep the curiosity alive
If a ball is thrown upwards, it slows down, stops momentarily, and then falls back to the ground. Name the forces acting on the ball and specify their directions.
(i)
During its upward motion
(ii)
During its downward motion
(iii)
At its topmost position
Q6
Keep the curiosity alive
A ball is released from the point P and moves along an inclined plane and then along a horizontal surface as shown in the Fig. 5.16. It comes to stop at the point A on the horizontal surface. Think of a way so that when the ball is released from the same point P, it stops (i) before the point A (ii) after crossing the point A .
Q7
Keep the curiosity alive
Why do we sometimes slip on smooth surfaces like ice or polished floors? Explain.
Q8
Keep the curiosity alive
Is any force being applied to an object in a non-uniform motion?
Q9
Keep the curiosity alive
The weight of an object on the Moon becomes one-sixth of its weight on the Earth. What causes this change? Does the mass of the object also become one-sixth of its mass on the Earth?
Q10
Keep the curiosity alive
Three objects 1,2 , and 3 of the same size and shape but made of different materials are placed in the water. They dip to different depths as shown in Fig. 5.17. If the weights of the three objects 1,2 , and 3 are
w
1
,
w
2
\mathrm{w}_{1}, \mathrm{w}_{2}
w
1
,
w
2
, and
w
3
\mathrm{w}_{3}
w
3
, respectively, then
(i)
w
1
=
w
2
=
w
3
\mathrm{w}_{1}=\mathrm{w}_{2}=\mathrm{w}_{3}
w
1
=
w
2
=
w
3
(ii)
w
1
>
w
2
>
w
3
\mathrm{w}_{1}>\mathrm{w}_{2}>\mathrm{w}_{3}
w
1
>
w
2
>
w
3
(iii)
W
2
>
W
3
>
W
1
\mathrm{W}_{2}>\mathrm{W}_{3}>\mathrm{W}_{1}
W
2
>
W
3
>
W
1
(iv)
W
3
>
W
1
>
W
2
\mathrm{W}_{3}>\mathrm{W}_{1}>\mathrm{W}_{2}
W
3
>
W
1
>
W
2
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Chapter overview
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Important Points
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