**16. **If the fraction of the atoms of a radioactive material left after 120 years is 1/64, what is the half-life of the material?

**A.**24 years**B.**20 years**C.**10 years**D.**2 years

**Correct Option: Answer is B**

**17. **A certain radioactive source emits radiation that was found to be deflected by both magnetic and electric and electric fields. The radiation is?

**A.**beta rays**B.**gamma rays**C.**x-rays**D.**ultra-viola rays

**Correct Option: Answer is A**

**18. **The inner diameter of a test tube can be measured accurately using a—-

**A.**micrometer screw gauge**B.**pair of dividers**C.**meter rule**D.**pair of vernier calipers

**Correct Option: Answer is D**

**19. **Two bodies have masses in the ratio3:1. They experience forces that impart to their acceleration in the ratio2:9 respectively. Find the ratio of forces the masses experienced

**A.**1:4**B.**2:1**C.**2:3**D.**2:5

**Correct Option: Answer is C**

**20. **Particles of mass 10^{−2}kg is fixed to the tip of a fan blade which rotates with angular velocity of 100rad^{−1}. If the radius of the blade is 0.2m, the centripetal force is?

**A.**2N**B.**20N**C.**200N**D.**400N

**Correct Option: Answer is B**

- Given

m = 10^{−2}

w = 100rads^{−1}

F = mw2r

r = 0.2m

F = ? - = 10
^{−2}x (100)^{2}x 0.2 - = 20N

**21. **A lead bullet of mass 0.05kg is fired with a velocity of 200ms^{−1}into a block of mass 0.95kg. Given that the lead block can move freely, the final kinetic energy after impact is?

**A.**50J**B.**100J**C.**150J**D.**200J

**Correct Option: Answer is A**

**22. **A ball of mass 0.1kg is thrown vertically upwards with a speed of 10ms^{−1}from the top of a tower 10m high. Neglecting air resistance, its total energy just before hitting the ground is? (Take g = 10ms^{−2})

**A.**5J**B.**10J**C.**15J**D.**20J

**Correct Option: Answer is B**

- m = 0.1kg

u = 10ms^{−1}

h = 10m

g = 10ms^{−2} - At h
_{max}; v = 0 - Using

v̸= u̸= g̸t

0= w̸- /10t - v
^{2}= u^{2}– 2gh

0^{2}= 10^{2}– 2 x 10h

20h = 100

h = 5m

Total height = 10 + 5

= 15m

Total energy = mghr = 0.1 x 10 x1 5

= 15J

**23. **A car of mass 800kg attains a speed of 25m/s in 20secs. The power developed in the engine is

**A.**1.25 x 10^{4}W**B.**2.50x 10^{4}W**C.**1.25 x 10^{6}W**D.**2.50 x 10^{6}W

**Correct Option: Answer is B**

- P = mv
^{2}/t= 800×25×25 / 20 - =>2.5 x 10
^{4}W

**24. **When the breaks in a car are applied, the frictional force on the tyre is?

**A.**a disadvantage because it is in the direction of the motion of the car**B.**a disadvantage because it is in the opposite direction of the motion of the car**C.**an advantage because it is in the direction of the motion of the car**D.**an advantage because it is in the opposite direction of the motion of the car

**Correct Option: Answer is D**

**25. **If the stress on a wire is 107NM^{−2}and the wire is stretched from its original length of 10.00 cm to 10.05 cm. The young’s modulus of the wire is?

**A.**5.0 x 10^{−4}Nm^{−2}**B.**5.0 x 10^{−5}Nm^{−2}**C.**2.0 x 10^{−8}Nm^{−2}**D.**2.0 x 10^{−9}Nm^{−2}

**Correct Option: Answer is D**

**26. **A solid weighs 10.00N in air, 6N when forcefully immersed in water, and 7.0N when fully immersed in a liquid, X. Calculate the relative density of the liquid X.

**A.**5/3**B.**4/3**C.**3/4**D.**7/10

**Correct Option: Answer is C**

**27. **When the temperature of a liquid increases, its surface tension

**A.**decreases**B.**increases**C.**remains constant**D.**increases then decreases

**Correct Option: Answer is A**

**28. **of its volume. What will be its pressure if the magnitude of its original temperature T is constant?

**A.**p_{0}/5**B.**4p_{0}/5**C.**p_{0}**D.**5P_{0}

**Correct Option: Answer is D**

**29. **A piece of substance of specific head capacity 450Jkg^{−1}k^{1}falls through a vertical distance of 20m from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat. [g = 10ms^{−2}]

**A.**29ºC**B.**49ºC**C.**92ºC**D.**94ºC

**Correct Option: Answer is B**

- mc△θ= mgh
- △θ= gh/c=10×2/0450=4/9ºC

**30. **A liquid boils when its saturated vapor pressure is equal to the external pressure

II. Dissolved substances in pure water lead to an increase in the boiling point.

III. When the external pressure is increased, the boiling point increases.

IV. Dissolved substances in pure water decreases the boiling point

Which of the above combinations are peculiarities of the boiling point of a liquid?

**A.**I, II and III only**B.**I, II, III, and IV**C.**I, II, and IV**D.**II, III, and IV