STD-8 SUB-SCIENCE

Class: VIIIScience AssignmentCHAPTER 12FRICTION

Q-1 Fill in the blanks

(1) Force opposing the motion is called the -------------------------.

(2) Friction depends upon the --------------- and ------------------- of the surface.

(3) Friction -------------- with pressure.

(4) Wheels ------------------ friction.

(5) ----------------- are substances which can reduce friction.

(6) The frictional force exerted by fluids is also known as ------------.(7) Frictional force in fluids depend upon --------, --------, and ------------- of the object.

(8) ---------------- objects offer less friction in fluids.

(9) A force which counter balance the applied force on body is ----------------.

(10) A force exerted by fluid on the object immersed in it, is called --------- ---------.

Q-2 Answer the following questions(1) What is a spring balance?

(2) Why are tyres made circular?

(3) Which is smoother: wet muddy or cemented floor?

(4) What is friction?

(5) Why a rolling ball stops after some time?

(6) It is difficult to move a cycle along a road with its brakes on. Why?

(7) In which direction the force of friction acts?

(8) Give some examples of force of friction.

(9) Write one advantage and disadvantage of friction.