Home › NEET UG › physics › Work, Energy and Power › A delivery boy raises a $10$ kg sack to a $2$ m …
A delivery boy raises a $10$ kg sack to a $2$ m shelf in $4$ s. The power expended (using $g = 10$ m/s$^2$) is:
A$10$ W, ignoring the height factor in the lift
B$200$ W, equal to the total work without dividing by time
C$80$ W, since $P = mgh$ alone gives this for the shelf
D$50$ W, since $P = mgh/t = 200/4 = 50$ W
Answer & Solution
Correct answer: D. $50$ W, since $P = mgh/t = 200/4 = 50$ W
$W = mgh = 200$ J; $P = W/t = 200/4 = 50$ W.
Related questions
A particle moves under a force F = −k x. The motion is:In a perfectly inelastic collision between two bodies:A spring with spring constant k is compressed by x. The elastic potential energy stored isIn a one-dimensional elastic collision between a moving body and an equal-mass stationary Two bodies of masses m₁ and m₂ have equal kinetic energies. The ratio of their momenta p₁/A pump lifts water at a rate of 3000 kg per minute through 30 m (g = 10 m s⁻²). The minimuA 60 W bulb burns for 2 hours. The total energy consumed in kWh is:A body is dropped from height h. Just before it hits the ground, its speed is: