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Physics Form 4 Chapter 2 Force and Motion I
big momentum. This causes a big momentum
Solution
Let the time taken by trolley A to move 40 cm with the same magnitude that moves the plane
forward.
be t seconds, and at the same time trolley B has
moved d cm. By taking the direction travelled by 4. Satellites and space capsules use air jets to
A as positive,
40 –d control movement and position. This is based
 1.5 × t  + (1.0 ×  t  = 0 on the principle of conservation of momentum
(1.5 × 40) – d = 0 for the case of explosion.
d = 60 cm

Applications of the Principle of
Conservation of Momentum in Daily
Life
Chapter
2
1. In the field of sports and games like billiard,
bowling, and carrom, the principle fo
conservation of momentum is involved in
collision form whereas in shooting, the Figure 2.67 Water sprinkler system
principle is involved in explosion.
5. A water sprinkler system uses this principle
2. In the launching of rocket, the combustion to irrigate plants in a farm. The whole area can
of fuel and oxygen produces a big downward be irrigated by the rotating sprinkler.
momentum and the rocket moves upwards
with the same magnitude of momentum. The 6. Some animals like the octopus uses this
momentum is conserved and is equal to zero. principle to move by squirting out a liquid
from its body.

7. This principle is also used to explain the
following situation:
(a) When a bullet comes out of a gun with
a high velocity, the gun recoils in the
opposite direction.
Jet engine
(b) A few firemen are required to hold the
Figure 2.66 Jet engine in a fighter jet hose in place when it is jetting a huge
volume of water with a high velocity. This
3. The jet engine of an airplane uses this principle is because a big backward momentum is
to produce a forward thrust. Air is sucked into produced.
the engine, compressed and heated. Fuel is
then injected into the mixture and combustion (c) In swampy areas, huge fans are used to
occurs. The burnt gas rushing out of the propel the boats forward.
exhaust has a very high velocity and hence a

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