Define watt. Express kilowatt in terms of joule per second. A 150 kg car engine develops 500 W for each kg. What force does it exert in moving the car at a speed of 20 m/s ?

A machine gun of mass 20 kg fires 35 gram bullet at the rate of 50 bullets per second with a speed of 400 m s^-1 . What force must be applied to the gun to keep it in position?

A car of mass 1000 kg moving with a velocity of 36 km/h comes to rest in 5 seconds. What is the force exerted on the car?

6xx10^(22) gas molecules each of mass 10^(-24)kg are taken in a vessel of 10 litre. What is the pressure exerted by gas molecules ? The root mean square speed of gas molecules is 100 m//s .

A motor car is fitted with a convex driving mirror of focal length 20 cm. A second motor car 2 m board and 1.6 m high is 6 m away from the first car. If the second car is overtaking at a relative speed of 14ms^-1 , how fast will the image be moving and in what direction?

A police van moving on a highway with a speed of 30 km h^-1 fires a bullet at a thiefs car speeding away in the same direction with a speed of 192 km h^-1 . If the muzzle speed of the bullet is 150 m s^-1 with what speed does the bullet hit the thiefs car ? (Note: Obtain that speed which is relevant for damaging the thief s car).

On complete combustion a litre of petrol gives off heat equivalent to 3 xx 10^7 J . In a test drive a car weighing 1200 kg, including the mass of driver, runs 15 km per litre while moving with a uniform speed on a straight track. Assuming tha friction offered by the road surface and air to be uniform, calcuate the force of friciton acting on the car during the test drive, if the efficiency of the car engine were 0.5.

Two persons manage to push a motor car of mass 1,200 kg at uniform velocity on the road. The same motor can be pushed by three persons to produce an acceleration of 0.2 ms^(-2) . With what force does each person push the motor car ?( Assume that all persons push motor car with same muscular effort.)

A rain drop of radius 2 mm falls from a height of 500 nr above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey ? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is 10 m s^-1 ?

Define magnetic field. Write an expression for force on a charge q moving with velocity vecv in a region having uniform magnetic field strength vecB . How does the speed change as the charge moves? Under what circumstances the force vecF will be zero and maximum? also obtain S.I. unit of the strength of magnetic field. Also give dimensional formula of B.