Give reasons for the following statements-
(a) 'Snow shoes' are more effective than ordinary shoes for walking on
snow.
(b) Porters place a large round piece of cloth on their heads when they
carry heavy loads.
(c) A sharp knife cuts vegetables and fruits more effectively than a blunt
knife.
(d) School bags are provided with wide straps to carry them.
(e) It is much easier to burst an inflated balloon with a needle than
(directly) with the finger.
(f) Mountaineers may suffer from nose bleeding at high altitudes.
(g) Airplanes have pressurised cabins for passenger safety while flying high
in the atmosphere.
Answers
Answer:
a) Snowshoes have a greater surface area in contact with the snow due to which there is less pressure on the snow. Due to this the snowshoes do not sink much in snow and it is easy to walk on it.
b) By placing the large round piece of cloth on their head, the porter increases the area of contact of load on their head. This decreases the pressure on the head and hence makes it easier to carry heavy loads.
c) A sharp knife cuts vegetables and fruits more efficiently than a blunt knife because the surface area of the knife is lesser than the blunt knife. Decreased surface area causes larger pressure.
d) Increased surface area means decrease in pressure, hence to make the school bags lighter and reduce the weight over shoulders, school bags are provided with wide straps to carry them.
e) A needle has lesser surface area than a finger. The decrease in surface area causes increase in the pressure hence it is much easier to burst an inflated balloon with a needle.
f) As we climb higher in the air, the air pressure decreases, Breathing becomes difficult in higher altitudes. Therefore, mountaineers may sometimes suffer from nose bleeding.
g) At higher altitudes where atmospheric pressure is very less breathing becomes difficult. Nose bleeding may also occur sometimes. Thus, the passenger cabins are pressurized so that passengers can feel comfortable while flying.