Thrust and Pressure Questions in English

(B) It is difficult to hold a school bag with a thin strap because the pressure exerted on the shoulders is very high.
Pressure is defined as force per unit area,given by the formula $P = F/A$.
Since pressure is inversely proportional to the surface area $(A)$ on which the force $(F)$ acts,a smaller surface area results in a higher pressure.
In the case of a thin strap,the contact surface area is very small,which leads to a significantly larger pressure on the shoulder,causing pain and discomfort.

(B) Pressure $(P)$ is defined as force $(F)$ divided by the area $(A)$ over which it acts,given by the formula $P = F/A$.
Since the weight of the box (force) remains constant in all three cases,the pressure is inversely proportional to the surface area $(P \propto 1/A)$.
To obtain the maximum pressure,the surface area of the base must be the minimum.
The three possible base areas are:
$1$. Length $\times$ Breadth = $60 \,cm \times 40 \,cm = 2400 \,cm^2$
$2$. Breadth $\times$ Width = $40 \,cm \times 20 \,cm = 800 \,cm^2$
$3$. Width $\times$ Length = $20 \,cm \times 60 \,cm = 1200 \,cm^2$
Comparing these,the minimum area is $800 \,cm^2$,which occurs when the breadth and width form the base.
Therefore,the pressure is maximum when the breadth and width form the base.

(B) On normal sand,the weight of a heavy animal or person is counterbalanced by the normal reaction force provided by the ground,allowing them to stand or walk on it.
However,quicksand consists of very fine,smooth particles saturated with water or air,which behave like a fluid.
Because of this fluid-like nature,the sand cannot provide a sufficient upward reaction force to support the weight of the object.
Consequently,the animal or person is likely to sink into the quicksand.