```224. Detergents dissolved in water help in cleaning clothes by :
(a) increasing the temperature of water
(b) reacting chemically with dirt
(c) reducing the surface tension of water"
(d) dissolving dirt
Ans : (c)
225. A boat loaded with rocks floats in the middle of a swimming pool and a man in the boat throws rocks over board in water. The
water level of the pool will :
(a) rise
(b) be lowered
(c) remain unchanged
(d) first rises then goes down
Ans : (b)
226. If a pendulum clock be taken from the earth to a revolving artificial satellite, it will : [IAS 2003]
(a) run slow
(b) run fast
(c) give the same time"
(d) stop altogether
Ans : (d)
227. A remote control gadget (for TV etc.) has in it:
(a) a small electromagnet, that emits electromagnetic waves
(b) a small oscillator that emits electric pulses
(c) a small transmitter that emits infrared signals
(d) None of the above
Ans : (c)
228. In, storms, the roofs of some houses are carried away. This is in accordance with:
(a) Bernoulli"s principle
(b) Archimedes" principle
(c) Law of inertia
(d) Pascal"s law
Ans : (a)
229. In Newton"s third law, the action and reaction forces:
1) act on different bodies.
2) act on the same body.
3) are not always equal.
4) are always equal.
Choose the correct answer from the codes given below:
(a)  1 and 3
(b)  1 and 4
(c)  2 and 4
(d)  2 and 3
Ans : (b)
230. A rocket and a jet engine differ because:
A. their working principles are entirely different.
238
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