Work, Energy and Power MCQ (NEET, JEE Main) – Test 2

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies 3.8 × 10⁷ J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. Take g = 9.8 ms^–2 [JEE (Main) 2016]

Two similar springs P and Q have spring constants K_P and K_Q such that K_P > K_Q. They are stretched first by the same amount (case a), then by the same force (case b). The work done by the springs W_P and W_Q are related as, in case (a) and case (b), respectively [AIPMT 2015]

A ball is thrown vertically downwards from a height of 20 m with an initial velocity v₀². It collides with the ground, loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity v₀ is (Take g = 10 ms^–2) [AIPMT 2015]

A block of mass 2 kg is free to move along the x-axis. It is at rest and from t = 0 onwards it is subjected to a time-dependent force F(t) in the x direction. The fore F(t) varies with t as shown in the figure. The kinetic energy of the block after 4.5 seconds is [IIT JEE 2010]

Two small particles of equal masses start moving in opposite directions from a point A in a horizontal circular orbit. Their tangential velocities are v and 2v respectively, as shown in the figure. Between collisions, the particles move with constant speeds. After making how many elastic collisions, other than that at A, these two particles will again reach the point A? [IIT JEE 2009]