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

Answer:

To accelerate an object we have to apply force. To apply force, we need to do work. When work is done on an object, energy is transferred and the object moves with a new constant speed. The energy that is transferred is known as kinetic energy and it depends on the mass and speed achieved.

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.

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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.