Question

A man has a box of mass 10 kg. The energy of the box, when the man runs with a constant velocity of
2m/s along with the box behind the bus is
a) 103
b) 30
c) 20 )
d) 2J​

Answer 1

Given :

• Mass of box = 10 kg
• Velocity of box = 2 m/s

To Find :

• Kinetic Energy of box

Solution :

We have formula for Kinetic Energy :

$\large\implies {\boxed{\sf\green{K.E \: = \: \dfrac{1}{2} mv^2}}}$

$\implies {\sf{K.E \: = \: \dfrac{1}{2} \: \times \: 10 \: \times \: 2^2}}$

$\implies {\sf{K.E \: = \: \dfrac{1}{2} \: \times \: 10 \: \times \: 4}}$

$\implies {\sf{K.E \: = \: \dfrac{1}{2} \: \times \: 40}}$

$\implies {\sf{K.E \: = \: 20}}$

$\large\therefore{\underline{\bf \orange{ Kinetic \: Energy \:of \: box\: is \: 20 \: J}}}$

Answer 2

Answer:

$\red{\textbf{Answer :- (c) 20 J }}$

Step-by-step explanation:

$\red{\textbf{Given :-}}$

$\textsf{mass of box = 10kg}$

$\textsf{velocity = 2m/s}$

$\red{\textbf{To find :-}}$

$\textsf{the energy of the box}$

$\textsf{so ,}$

$\textsf{when the man runs with the box }$

$\textsf{m = 10 kg }$

$\textsf{it gains KE as, }$

$KE = \LARGE\frac{1}{2} \small {mv}^{2}$

$= \LARGE\frac{1}{2} \small \times 10 \times (2 {)}^{2}$

$= 20j$

$\textsf{so , The energy of the box is 20 J}$

$\textsf{hence option c is the right Answer}$

$\red{\textbf{More information :- }}$

• Kinetic energy is directly proportional to the mass of the object and to the square of its velocity.

$KE = \LARGE\frac{1}{2} \small {mv}^{2}$

• KE = kinetic energy
• m = mass of a body
• v = velocity of a body