Chapter 5 Solutions — Exploring Forces

Keep the Curiosity Alive

1. 1.
   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…
2. 2.
   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.
3. 3.
   Two balloons rubbed with a woollen cloth are brought near each other. What would happen and why?
4. 4.
   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.
5. 5.
   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
6. 6.
   A ball is released from the point P and moves along an inclined plane and then along a horizontal surface as shown in 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.
7. 7.
   Why do we sometimes slip on smooth surfaces like ice or polished floors? Explain.
8. 8.
   Is any force being applied to an object in a non-uniform motion?
9. 9.
   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?
10. 10.
    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, and w_3, respectively, then

    • (i) w1 = w2 = w3
    • (ii) w1 > w2 > w3
    • (iii) w2 > w3 > w1
    • (iv) w3 > w1 > w2