Exercise 3

Question 21 :

Natural radioactivity was discovered by


A). Marie Curie
B). Ernest Rutherfor
C). Henri Becquerel
D). Enrico Fermi
Answer : Option C

Question 22 :

Planets are


A). luminous heavenly bodies revolving around a star
B). non-luminous heavenly bodies
C). luminous heavenly bodies that twinkle
D). luminous heavenly bodies that do not twinkle
Answer : Option B

Question 23 :

One nanometer is equal to


A). 10-6m
B). 10-8m
C). 10-9m
D). 10-5m
Answer : Option C

Question 24 :

Mica is used in electrical appliances such as electric iron because mica is


A). a good conductor of heat but a bad conductor of electricity
B). a bad conductor of heat but a good conductor of electricity
C). a good conductor of heat as well as electricity
D). a bad conductor of heat as well as electricity
Answer : Option A

Question 25 :

It is easier to roll a barrel full of coal tar than to pull it because


A). the full weight of the barrel comes into play when it is pulled
B). the rolling friction is much less than the sliding friction
C). more surface area of the barrel is in contact with the road when it is pulled
D). coal tar is a liquid and it flows in the barrel when it is rolled
Answer : Option B