SCIENCE CLASS VIII

TIME: – 1HR                                       F.M.:- 25

TOPICS: –
Friction
Microorganisms: Friend and Foe

Q1. Each question carries 1mark.
(i) 
Microorganisms are classified into four major groups. Name them.
(ii)  Several diseases like tuberculosis, smallpox and hepatitis can be prevented by ___________.
(iii) Define pasteurization.
(iv) Friction depends on the ________ of surfaces.
(v)  Give two ways to increase friction?

Q2. Each question carries 2marks.
(i)
Write short notes on           A. Protozoa            B. Algae
(ii) Define the process of fermentation and its application.
(iii) Write short notes on medicinal use of microorganisms.
(iv) Find the net force acting on an object whose mass is 2 kg, as shown in figure.
(v) Explain why sliding friction is less than static friction.

Q3. Each question carries 3marks.
(i) What are the major precautions one should follow while taking antibiotics?
(ii) Explain how microbes are useful to us in our day to day life.
(iii) Explain increasing and reducing friction.
(iv) What is fluid friction? Write the factors on which fluid friction depends.
(v) Explain why objects moving in fluids must have special shapes.

Q4. Each question carries 5marks.
(i)
  What are the major group of microorganisms explain each group with their harmful and useful effects in our life?
(ii) Explain nitrogen cycle with a diagram.
(iii) Explain the reason.  2+2+1
A.  Force of friction increases when two surfaces are pressed harder.
B. While travelling on a rickshaw, you might have experienced that if the seat cover is very smooth, you tend to slip when brakes are applied suddenly.
C. The handle of a cricket bat or a badminton racquet is usually rough.
(iv) Give examples to show that friction is both a friend and foe.

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