Friction Worksheet-3

Friction Worksheet-3

1. Suppose your writing desk is tilted a little, a book kept on it starts sliding down. Show the direction of frictional force acting on it.

2. You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk or run on the floor? Why?

3. Explain why sportsmen use shoes with spikes.

4. A has to push a lighter box and B has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?

5. Explain why sliding friction is less than static friction.

6. Give examples to show that friction is both a friend and a foe.

7. Explain why objects moving in fluids must have special shapes.

8. What is force of friction?

9. Is the friction the same for all the surfaces?

10. Does friction depend on the nature of objects?

Answer:

1. The book moves downwards. The frictional force is acting opposite to the movement of book. So it acts upwards.

2. The layer of soap makes floor smooth due to which the friction is reduced and the foot cannot make a proper grip on the floor. Therefore it is difficult to walk on a soapy floor and we start to slip on the floor.

3. Sportsmen use shoes with spike to increase the friction between shoes and surface. The shoes with spike do not slip while they run or play.

4. The heavy object will be pressed hard against the opposite surface and produces more friction. So B will have to apply a larger force due to more friction.

5. The two sliding objects find less time to get interlocked against each other. So they get less friction. Therefore sliding friction is always less than static friction.

6. Examples to show that friction is a friend and a foe:

Friction is friend:

(i) Friction allows us to grip and catch different objects. For example one player is throwing ball towards other and other person can catch it easily.

(ii) It helps us to walk comfortably on the surface or ground. If there were no friction we could not walk and we could slip.

(iii) It helps to minimize the speed or to stop the moving objects.

(iv) It helps us to write on paper or blackboard. If there were no friction the pen or chalk would slide on paper or board and we could not write any thing.

(v) The things do not move from their places if we do not want due to friction. If there were no friction it would have been difficult to place the object at one place, they would move here and there

Friction is foe:

(i) Friction causes wear and tear and continuous maintenance of the objects and machines.

(ii) It damages the parts of machines.

(iv) It reduces the speed of moving objects so more force is required. For example it is difficult to move up on the hill by car.

(v) It does not allow the free movement of objects.

7. The object moving in fluids must have a special shape called streamlined shape. It helps to overcome the friction between objects and fluids. The objects have pointed fronts with little broader middle portion which gets tapered at the back.

8. The force acting on a moving body which is equal and opposite to the direction of motion is called force of friction.

9. No

10. Yes