A steam engine delivers `5.4 xx 10^8`J of work per minute and services `3.6 XX 10^8` J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?

9.363xx10^19 electrons pass,through an area per minute. What is,the electric current?

A person trying to lose weight (dieter) lifts a 10 kg mass, one , thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated, (a) How much work does she do against the gravitational force? (b) Fat supplies 3.8 xx 10^7 J of energy per kilogram which is converted to mechanical energy with a 20% efficiency rate. How much fat will the dieter use up?

A trolley of mass 200 kg moves with a uniform speed of 36 km/ h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 m s^-1 relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. What is the final speed of the trolley? How much has the trolley moved from the time the child begins to run?

A geyser heats water flowing at the rate of 3.0 litres per minute from 27^@ C to 77 ^@C . If the geyser operates on a gas burner. What is the rate of consumption of the fuel if its heat of combustion is 4.0×10 4 J/g?

In Millikan’s oil drop experiment, what is the terminal speed of an uncharged drop of radius 2.0 xx 10^-5m and density 1.2 xx 10^3 kg m^-3 ? Take the viscosity of air at the temperature of the experiment to be 1.8 xx 10^-5 Pa s. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to air.

A car is moving from rest, After 10 seconds its wheels rotate 360 times in 1 minute. If the radius of the wheel is 50cm, then find the linear distance travelled in 6 minutes.

A copper wire has diameter 0.5 mm and resistivity of 1.6 xx 10^-8Omega m. What will be the length of this wire to make its resistance 10Omega ? How much does the resistance change if the diameter is doubled?

In changing the state of a gas adiabaticaiiy from an equilibrium state A to another equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in the latter case? (Take 1 cal = 4.19 J)