A boy of mass 50 kg runs up to a stair case of 45 steps in 9 s. If the height of a 15 cm, find his power.

A man of mass 60 kg walks up to the top of a building of height 15 m. Calculate the increase in potential energy.

Find the force required to move a train of mass 5000 quintals up an incline of 1 in 50 with an acceleration 2ms^-2 . Take force of friciton = .2N/s qunital and g = 10ms^-2 .

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 (a) climbs up with an acceleration of 6 m s^2 (b) climbs down with an acceleration of 4 m s^2 (c) climbs up with a uniform speed of 5 m s^1 (d) falls down the rope nearly freely under gravity? (Ignore the mass of the rope).

:A 10 kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50% of power is used up in heating the machine itself or lost to the surroundings. Specific heat of aluminium = 0.91 J g^-1 K^-1 .

A bucket made up of metal sheet is in the form of a frustum of height 16 cm (closed at the lower end but open at the upper end) with radii of the lower and upper ends are 8 cm and 20 cm respectively. Find the cost of the bucket if the cost of the metal sheet used is ₹ 15.00 per 100 cm (pi = 3.14) .

A mass of 5.0 kg is pulled along a horizontal plane by a force in a direction making an angle 45° with the horizontal.The body moves with uniform velocity through a distance of 10 metre. Find the work done by the force(Co-efficient of firction=0.3).

A ball of mass 1.2 kg moving with velocity 20cm/s collides with another body of equal mass at rest.Find the loss of K.E of the system,assuming that co -efficient of restitutionis 0.6.

The terminal velocity of a copper ball of radius 2.0 mm falling through a tank of oil at 20^@C is 6.5 cm/s. Compute the viscosity of the oil at 20^@C . Given, rho_(oil) = 1.5 xx 10^3 kg//m^3, rho_(copper) = 8.9 xx 10^3 kg//m^3 .

A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. if 4.0 kg of ice is put in the box, estimate the amount of-ice remaining after 6 h. The outside temperature is 45 ^@C , and co-efficient of thermal conductivity of thermacole is 0.01 J s^-1.m-^1 K-^1 . [Heat of fusion of water = 335 x 103 J kg^-1

A far sighted person has his near point 50 cm. Find the power of lens he should use to see at 25 cm clearly.