Chapter 7 – Work, Energy and Power

A body of mass 1 kg of thrown upwards with a velocity 20 m/s. It momentarily comes to rest after attaining a height of 18m. How much energy is lost due to air friction ? (g=10m/s^2) A body of mass 1 kg of thrown upwards with a velocity 20 m/s. It momentarily comes to rest [...]

A uniform force of (3i^+j^​) newton acts on a particle of mass 2 kg. Hence the particle is displaced from position (2i^+k^) meter to position (4i^+3j^​−k^) meter. The work done by the force on the particle is A particle moves from a point (-2i^ + 5j^) to (4j^ + 3k^ ) when a force of [...]

Two similar spring P and Q have spring constants KP​ and KQ​, such that KP ​ KQ​. They are stretched, first by the same amount (case a), then by the same force (case b). The work done by the spring WP​ and WQ​ are related as, in case (a) and case (b), respectively: first by [...]

A particle moves from a point (-2i^ + 5j^) to (4j^ + 3k^ ) when a force of (4i^+3j^) N is applied. How much work has been done by the force ? A particle moves from a point (-2i^ + 5j^) to (4j^ + 3k^ ) when a force of (4i^+3j^) N is applied. How [...]

Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take ‘g’ constant with a value 10 m/s^2. The work done by the (i) gravitational force the (ii) resistive force of airs is: A particle of mass m [...]

Water falls from a height of 60 m at the rate 15 kg/s to operate a turbine. The losses due to frictional forces are 10% of energy . How much power is generated to by the turbine? (g=10 m/s^(2)`. Water falls from a height of 60 m at the rate 15 kg/s to operate a [...]

An engine pumps water through a hose pipe . Water passes through the pipe and leave with a velocity 2m/s. The mass per unit length of water in pipe is 100 kg/m . What is the power of the engine ? An engine pumps water through a hose pipe . Water passes through the pipe [...]

The heart of a man pumps 5 liters of blood through the arteries per minute at a pressure of 150 mm of mercury. If the density of mercury be 13.6 × 10^3 kg/m^3 and g = 10m/s^2, then the power of heart in watt is : The heart of a man pumps 5 liters of [...]

A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts from rest the force on the particle at time t is A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts from rest [...]

A body of mass 1 kg begins to move under the action of a time dependent force F = (2t i^ – 3t^2j^​) N, where i^ and j^​ are unit vectors along x and y axis. What power will be developed by the force at the time (t)? A body of mass 1 kg begins [...]