A boy is hanging from branch of a tree as shown. Angle between his arm, for tension to be maximum in arms must be ............ $^o$

If an inclined plane is made slowly horizontal by reducing its inclination with horizontal, the component of weight parallel to the plane of block resting on the inclined plane

An $80\, kg$ person is parachuting and is experiencing a downward acceleration of $2.8\, m/s^2$. The mass of the parachute is $5\, kg$. The upward force on the open parachute is  ........... $N$ (Take $g = 9.8\, m/s^2$)

Define force. What is contact force ? Write two example of field force.

A pebble of mass $0.05\; kg$ is thrown vertically upwards. Give the direction and magnitude of the net force on the pebble,

$(a)$ during its upward motion,

$(b)$ during its downward motion,

$(c)$ at the highest point where it is momentarily at rest.

Do your answers change if the pebble was thrown at an angle of $45^o$ with the horizontal direction? Ignore air resistance.

In the given arrangement, the normal force applied by block on the ground is