QQuestion
(a) Name the unit of work done used on the subatomic scale.
(b) To which class of lever does a pair of scissors belong?
(c) A stone is tied to a string and displaced from A to B by application of constant force F in three different ways as shown below.
Arrange the three cases in ascending order of the work done by the force. (Given AJB is a semicircle, θ < 90° and AB = 20 m)
✓Answer
(a) electron volt (eV)
(b) Class I lever
(c) Work done is W = Force × Displacement × cos θ.
In Case 1, force is perpendicular to displacement, so work done is zero.
In Case 2, force acts along displacement, so work done is maximum.
In Case 3, θ < 90°, so the work done is greater than Case 1 but less than Case 2.
Therefore, the ascending order is: Case 1 < Case 3 < Case 2.
Related Questions
More ICSE Moderate level questions
A ball of mass 20 g falls from a height of 45 m. It rebounds from the ground to a height of 40 m. Calculate: (a) initial potential energy of the ball. (b) the speed of the ball at which it hits the ground. (c) the loss in kinetic energy on striking the ground. [g = 10 m s−2]
A cyclist stops pedalling while moving along a frictionless hilly road. Which quantity remains constant? (a) Kinetic energy (b) Potential energy (c) Total mechanical energy increases (d) Total mechanical energy remains constant
The energy transformation that takes place during photosynthesis is: (a) heat energy to chemical energy (b) chemical energy to light energy (c) light energy to chemical energy (d) chemical energy to heat energy
Two identical marbles A and B are rolled down along Path 1 and Path 2 respectively. Path 1 is frictionless and Path 2 is rough. (a) Which marble will surely reach the next peak? (b) Along which path/s the mechanical energy will be conserved? (c) Along which path/s is the law of conservation of energy obeyed?
A force ‘F’ moves a load from A to C as shown in the figure below. For the calculation of the work done, which of these lengths would you use as the displacement? (a) 3 m (b) 4 m (c) 5 m (d) 7 m
A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate: (a) the work done by the engine. (b) the power of the engine.
Calculate the power spent by a crane while lifting a load of mass 2000 kg, at velocity of 1.5 m s−1. (g = 10 m s−2).
Sumit does 600 J of work in 10 min and Amit does 300 J of work in 20 min. Calculate the ratio of the powers delivered by them.
(a) What should be the angle between the direction of force and the direction of displacement, for work to be negative? (b) Name the physical quantity obtained using the formula , where U is the potential energy and h is the height.
The energy conversion in a washing machine is from ............... (a) magnetic to electrical (b) electrical to mechanical (c) electrical to magnetic (d) magnetic to electrical
When the speed of a moving object is doubled, then its kinetic energy: (a) remains the same (b) decreases (c) is doubled (d) becomes four times
Richa weighing 40 kgf leaves point P on her skateboard and reaches point Q on the ground with velocity 10 m s⁻¹. Calculate: (a) the kinetic energy of Richa at point Q (b) the vertical height of point P above the ground. (Use g as 10 m s⁻² and neglect friction.) (c) the kinetic energy of Richa at point R. (While moving from Q to R, she loses 500 J of energy against friction.)