Question

Define Kinetic Energy. Write expression for Kinetic Energy.A force of 12N acts on an

object of mass of 4kg in the state of rest for 3s. Calculate the kinetic energy acquired by the

object.​

Answer 1

Explanation:

Force = mass × acceleration

F = 12N

m= 4kg

then,

a = f/m = 12/4 = 3m/s^2

now,

u= 0

t= 3sec

v = u + at = 0+3×3 = 9 m/s

Answer 2

Kinetic Energy:

• It is a type of mechanical energy possessed by a body by the virtue of its motion.

• KE = ½ × m × v² , m is mass and v is velocity.

________________________

Let velocity of body after 3 sec be v :

$\rm\therefore \: v = u + at$

$\rm\implies\: v = u + (\dfrac{force}{mass} \times t)$

$\rm\implies\: v = 0+ (\dfrac{12}{4} \times 3)$

$\rm\implies\: v = 9 \: m {s}^{ - 1}$

Now, let kinetic energy be KE :

$\rm KE = \dfrac{1}{2} m {v}^{2}$

$\implies\rm KE = \dfrac{1}{2} \times 4 \times {(9)}^{2}$

$\implies\rm KE = 2 \times 81$

$\implies\rm KE = 162 \: joule$

So, KE is 162 Joules.