In a stack there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016 mm. What is the total thickness of the stack?

A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair?

A circular coil of wire consisting of 80 turns, each of radius 50 mm carries a current of 0.25 A. What is the magnetic field at the centre of the coil?

A wooden article was made by scooping out a hemisphere from each end of a solid cylinder. If the height of the cylinder is 20 cm and radius of the base is 3.5 cm, find the total surface area of the article.

A metre stick is balanced on a knife edge at its centre. When two coins, each of masb 5 g are put one on top of the other at the 12.0 cm mark, the stick is found to be balanced at 45.0 cm. What is the mass of the metre stick?

Find the time in which a layer of ice 3 cm thick on the surface of a pond will increase in thickness by 1 mm when the temperature of the surrounding is -20°C .the thermal conductivity of ice is 2.1 W/m K, latent heatof ice 3.36 10^5J/kg and density is 900 kg/m^-3 .

A brass rod of length 50 cm and diameter 3.0 mm is joined to a steel rod of the same length and diameter. What is the change in length of the combined rod at 250 ^@C , if the original lengths are at 40.0 ^@C ? Is there a ‘thermal stress’ developed at the junction? The ends of the rod are free to expand (Co-efficient of linear expansion of brass = 2.0 xx 10^-5K^-1 steel = 1.2 xx 10^-5 K^-1) .

Two lenses of powers, 15D and +5D are in contact with each other forming a combination lens. What is the focal length of the combination?

A steel tape 1m long is correctly calibrated for a temperature of 27.0 ^@C . The length of a steel rod measured by this tape is found to be 63.0 cm on a hot day when the temperature is 45.0 ^@C . What is the actual length of the steel rod on that day? What Is the length of the same steel rod on a day when the temperature is 27.0 ^@C ? Coefficient of linear expansion of steel = 1.20xx10^-5 K^-1 .