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.
() Airplanes have pressurised cabins for passenger safety while flying high in the atmosphere.
Answers
(a) Snow shoes are more effective than ordinary shoes for walking on snow because they have
greater surface area in contact with snow duo to which it creates low pressure which do not sink much on walking on soft ice. So we can walk easily.
(b) By placing a thick pieces of clothes, porters increase the area of contact of load with their head.
Duo to which pressure of load decrease and it become easy to load.
(c) Because a sharp knife is lesser than burnt knife. So it is easy to cut vegetables.
(d) Because there weight may spread over large area producting less pressure on shoulder.
(e) The needle covered less area than finger. This helps the needle to exert more force.
(f) On higher altitudes air pressure decreases. This pressure is much less than pressure excerts by blood. So some vessels get burst and produce blood.
(g) because there is low pressure on higher altitudes. so it protect them from hypoxia.