Question

Answer the following questions in brief.
A. A plastic cube is released in water. Will it sink of come to the surface of watet?
B. Why do the load carrying heavy vehicles have large number of wheels?
C. How much pressure do we carry on our heads? why don't we feel it?

Answer 1

(a) The plastic cube is going to float on the surface of water as its density is less than that of water.

(b) We know, $\mathrm{Pressure}=\frac{\mathrm{Force}}{\mathrm{Area}}$
So, greater the area of contact between two surfaces, lesser will be the pressure. So, the load carrying heavy vehicles have large number of wheels so that the pressure on the road is reduced due to larger contact area. Also, using large number of wheels ensures that the force due to the load is shared among the tyres and no single tyre is under stress.

(c) We carry atmospheric pressure of about 10⁵ Pa on our heads. We don't feel it because this atmospheric pressure is balanced by the pressure created by the air and blood inside our body.