Common Forces in Mechanics

A monkey of mass $20 \mathrm{kg}$ is holding a vertical rope. The rope will not break when a mass of $25 \mathrm{kg}$ is suspended from it but will break if the mass exceeds $25 \mathrm{kg}$. What is the maximum acceleration with which the monkey can climb up along the rope? $\left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$

Two blocks of mass $2.9 \mathrm{kg}$ and $1.9 \mathrm{kg}$ are suspended from a rigid support $S$ by two inextensible wires each of length $1 \mathrm{m}$ see figure. The upper wire has negligible mass and the lower wire has a uniform mass of $0.2 \mathrm{kg}{\mathrm{m}}^{-1}$ . The whole system of blocks, wires and support has an upward acceleration of $0.2 \mathrm{m}{\mathrm{s}}^{-2}$ . Acceleration due to gravity is $9.8 \mathrm{m}{\mathrm{s}}^{-2}$ .

(i) Find the tension $T$ at the mid-point of the lower wire.

(ii) Find the tension  $T^{\text{'}}$  at the mid-point of the upper wire.

A man weighing $60 \mathrm{kg}$ is in a lift moving down with an acceleration of $1.8 \mathrm{m} {\mathrm{s}}^{-2}$. The force exerted by the floor on him is

A man weighing $60 \mathrm{kg}$ is in a lift moving down with an acceleration of $1.8 \mathrm{m} {\mathrm{s}}^{-2}$. The force exerted by the floor on him is

What are field forces? Give two examples.

A force is said to be variable if its magnitude or direction changes with position or time.

Mention the two ways to vary a variable force.

Our shoulder joint is a hinge joint. 

What is hinge force?

Field forces are also called _____ forces or at-a-distance forces.

What is the field force example?

Is gravity a field force ?

What is field force?

When a person walks on a surface, the frictional force exerted by the surface on the person is opposite to the direction of motion. True or false?

When walking on ice one should take short steps. Why?

There is a limit beyond which the polishing of a surface increases frictional resistance rather than decreasing it why?

A $14 \mathrm{kg}$ block is hanged using a system of pulleys as shown in figure. Tension in string connecting celling and topmost pulley is :-

A block of mass $m$ is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration $a$. The work done by tension on the block during $t$ seconds is $(u=0):$

Define viscous force.

Identify the hinge force among the following.