3.
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
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Answer:
(a) ‘Snow shoes’ are more effective than ordinary shoes for walking on snow.
Answer: Snowshoes are more effective than ordinary shoes for walking on snow, because the snow shoes are comparatively broader than the ordinary shoes. As we know that pressure is inversely proportional to the surface area which means that if area increases then pressure will decrease. So, the body weight will be distributed over a larger surface area of snow shoes and helps to walk effectively on snow.
(b) Porters place a large round piece of cloth on their heads when they carry heavy loads.
Answer: Porters place a large round piece of cloth on their heads when they carry heavy loads because by doing this, they increase the area of contact of the load with their heads and as we know that the pressure is inversely proportional to surface area so the pressure on their heads gets reduced.
(c) A sharp knife cuts vegetables and fruits more effectively than a blunt knife.
Answer: As the area of the sharp knife is less than that of the blunt knife thereby it increases the pressure while cutting vegetables and fruits, because pressure is inversely proportional to area. So, a sharp knife cuts vegetables and fruits more effectively than blunt knife.
(d) School bags are provided with wide straps to carry them.
Answer: School bags are provided with wide straps to carry them, because as we know that the pressure is inversely proportional to the contact area that is if the contact area increases pressure decreases. So wide straps will distribute the weight of the box over a larger area thereby decreasing pressure on our Shoulders.
(e) It is much easier to burst an inflated balloon with a needle than (directly) with the finger.
Answer: As needle has a smaller surface area than the finger, so the force applied by needle at almost a single point leading to a much larger pressure on the balloon. So, it is easier to burst an inflated balloon with needle than finger.
(f) Mountaineers may suffer from nose bleeding at high altitudes.
Answer: Atmospheric pressure on our body is balanced by our blood pressure. At Higher altitudes the air pressure/Atmospheric pressure reduces and it becomes lower than our blood pressure so delicate blood vessels in our nose burst sometimes resulting in the nose bleeding.
(g) Airplanes have pressurised cabins for passenger safety while flying high in the atmosphere.
Answer: As we know that at high altitudes, the atmospheric pressure decreases, so the low pressure can be highly uncomfortable for travellers. Due to this pressure in the aircraft cabin is increased to a sufficient value so as to safeguard the passengers.