A man of mass 70 kg stands on a weighing scale in a lift which is moving (b) downwards with a uniform acceleration of $5 m s^{-2}$,

Two bodies of masses 10 kg and 20 kg respectively kept on a smooth, horizontal surface are tied to the ends of a light string. A horizontal force $F = 600 N$ is applied to (ii) B along the direction of string. What is the tension in the string in each case?

Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg, (d) lying on the floor of a train which is accelerating with $1 m s^{-2}$, the stone being at rest relative to the train. Neglect air resistance throughout.

A monkey of mass 40 kg climbs on a rope (Fig. 5.20) which can stand a maximum tension of 600 N. In which of the following cases will the rope break: the monkey (d) falls down the rope nearly freely under gravity? (Ignore the mass of the rope).

A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. What is the tension in the string ? What is the maximum speed with which the stone can be whirled around if the string can withstand a maximum tension of 200 N ?

If, A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. What is the tension in the string ? What is the maximum speed with which the stone can be whirled around if the string can withstand a maximum tension of 200 N, the speed of the stone is increased beyond the maximum permissible value, and the string breaks suddenly, which of the following correctly describes the trajectory of the stone after the string breaks :

Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg, (a) just after it is dropped from the window of a stationary train,

Ten one-rupee coins are put on top of each other on a table. Each coin has a mass m. Give the magnitude and direction of (c) the reaction of the 6th coin on the 7th coin.

An aircraft executes a horizontal loop at a speed of 720 km/h with its wings banked at 15°. What is the radius of the loop ?

A pebble of mass 0.05 kg is thrown vertically upwards. Give the direction and magnitude of the net force on the pebble, (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° with the horizontal direction? Ignore air resistance.

A truck starts from rest and accelerates uniformly at $2.0 m s^{-2}$. At $t = 10 s$, a stone is dropped by a person standing on the top of the truck (6 m high from the ground). What are the (a) velocity of the stone at $t = 11s$ ? (Neglect air resistance.)

A batsman deflects a ball by an angle of 45° without changing its initial speed which is equal to 54 km/h. What is the impulse imparted to the ball ? (Mass of the ball is 0.15 kg.)

A man of mass 70 kg stands on a weighing scale in a lift which is moving (c) upwards with a uniform acceleration of $5 m s^{-2}$. What would be the readings on the scale in each case?

Explain why (d) a cricketer moves his hands backwards while holding a catch.

A train runs along an unbanked circular track of radius 30 m at a speed of 54 km/h. The mass of the train is $10^6$ kg. What provides the centripetal force required for this purpose — The engine or the rails ? What is the angle of banking required to prevent wearing out of the rail ?

A constant force acting on a body of mass 3.0 kg changes its speed from $2.0 m s^{-1}$ to $3.5 m s^{-1}$ in 25 s. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force ?

A man of mass 70 kg stands on a weighing scale in a lift which is moving (d) What would be the reading if the lift mechanism failed and it hurtled down freely under gravity ?

Figure 5.17 shows the position-time graph of a body of mass 0.04 kg. Suggest a suitable physical context for this motion. What is the time between two consecutive impulses received by the body ? What is the magnitude of each impulse ?

A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in Fig. 5.19. What is the action on the floor by the man in the two cases ? If the floor yields to a normal force of 700 N, which mode should the man adopt to lift the block without the floor yielding ?

2. SI unit of force is