Solve this: 
3. Give reasons for the following statements-
(a) 'Snow shoes' are more effective than ordinary shoes 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.

Dear student,
post multiple queries in different threads so that we can help you more efficiently,
The answers to some parts are below,
a) 
snow boots are broader..so they occupy a larger area ultimately reducing the pressure exerted on the ground (as area and pressure exerted are inversely proportional) which would help uh from not sinking in the snow.
Pressure = Force / Area.
Area of the snowshoe is large. So, the pressure acting on the snow is less and shoe does not sink in the snow.

b) 
The cloth on the head of porters acts as a cushion and increase the contact area between the load and the head. The increased area reduces the pressure on the head due to the heavy loads. This is according to the relation, P = F/A. An increase in area will decrease the pressure due to a force (load).
c) 
Sharpe knife exerts more pressure than the blunt knife.Pressure depends on the surface area.In a blunt knife, surface area is more so it exerts less pressure but a Sharpe knife has a very small surface area so it exert more pressure and cut object faster

Regards

 

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