Choose one or more correct alternatives.

a. For work to be performed, energy must be ....

(i) transferred from one place to another
(ii) concentrated
(iii) transformed from one type to another
(iv) destroyed

b. Joule is the unit of ...

(i) force
(ii) work
(iii) power
(iv) energy

c. Which of the forces involved in dragging a heavy object on a smooth, horizontal surface, have the same magnitude?

(i) the horizontal applied force
(ii) gravitational force
(iii) reaction force in vertical direction
(iv) force of friction

d. Power is a measure of the .......

(i) the rapidity with which work is done
(ii) amount of energy required to perform the work
(iii) The slowness with which work is performed
(iv) length of time

e. While dragging or lifting an object, negative work is done by

(i) the applied force
(ii) gravitational force

(iii) frictional force

(iv) reaction force

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Solution

a. For work to be performed, energy must be transferred from one place to another.

b. Joule is the unit of work and energy.

c. The gravitational force and the reaction force in vertical direction have same magnitude. Friction is not action as the horizontal surface is smooth.

d. Power is a measure of the rapidity with which work is done

e. While dragging or lifting an object, the negative work is done by frictional and gravitational force, respectively.

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Similar questions

A man is dragging a large trunk on the ground by applying a force at an angle ‘θ’ to the horizontal. The work done by i) gravity on the trunk, ii) man on the trunk & iii) frictional force on the trunk will be

(a) The S.I. unit of work is

(i) second (ii) metre

(iii) joule (iv) Newton.

(b) No work is done by a force if the body

(i) moves in direction of the force

(ii) does not move

(iii) moves in the opposite direction

(iv) none of these

(i) same by both coolies

(ii) is more by coolie A than by B

(iii) is less by coolie A than by B

(iv) nothing can be said

(d) The expression of power P is

(i) P = mgh (ii) P = $\frac{1}{2} m v^{2}$

(iii) P = $F \times d$ (iv) P = $F \times \frac{d}{t}$

(e) 1 H.P. is equal to

(i) 1 W (ii) 1 J

(iii) 764 J (iv) 746 W

(f) When a boy doubles his speed, his kinetic energy becomes

(i) half (ii) double

(iii) four times (iv) no change

(g) A boy lifts a luggage from height 2 m to 4m. The potential energy will become

(i) half (ii) double

(iii) one- third (iv) one - fourth

Rewrite the following sentences using proper alternative.

a. The potential energy of your body is least when you are .....

(i) sitting on a chair
(ii) sitting on the ground
(iii) sleeping on the ground
(iv) standing on the ground

b. The total energy of an object falling freely towards the ground ...

(i) decreases
(ii) remains unchanged

(iii) increases
(iv) increases in the beginning and then decreases

c. If we increase the velocity of a car moving on a flat surface to four times its original speed, its potential energy ....

(i) will be twice its original energy

(ii) will not change
(iii) will be 4 times its original energy
(iv) will be 16 times its original energy.

d. The work done on an object does not depend on ....

(i) displacement
(ii) applied force
(iii) initial velocity of the object
(iv) the angle between force and displacement.

Choose the correct option according to the angle between force and direction of displacement.

$\begin{matrix} Coloumn1 & Coloumn2 1. θ is zero & i) Work done is always zero 2. θ is less than 90^{0} & ii) Work done is non-negative 3. θ is greater than 90^{0} & iii) Work done is always positive 4. θ is 90^{0} & iv) Work done is never positive \end{matrix}$

Q. A 5 kg block is lifted vertically through a height of 5 metre by a force of 60 N.
Determine:
(i) The work done by applied force in lifting the block,
(ii) The potential energy of the block at 5 m,
(iii) The kinetic energy of the block at 5 m,
(iv) The velocity of the block at 5 m.

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