Question

The potential energy of a catapult was completely converted into kinetic energy by releasing a small stone with a mass of 20 grams. The velocity of the stone when it reached the target was 15.0 meters/second. What was the value of the kinetic energy of the stone when it reached the target?

Answer 1

Answer: 2.25 J

Explanation: Kinetic energy is the energy possessed by an object by virtue of its motion.

$K.E=\frac{1}{2}\times mv^2$

m= mass of object= 20 g = 0.02 kg     (1 kg= 1000 g)

v= velocity of object= 15 m/s

$K.E=\frac{1}{2}\times 0.02\times 15^2=2.25kgm^2s^{-2}=2.25J$

$(1J=1kgm^2s^{-2})$

Answer 2

1,000 grams = 1 kilogram
20 grams = 0.02 kilogram

Kinetic energy = (1/2) (mass) x (speed)²

                           (1/2) (0.02) x (15)² =

                                 (0.01)  x  (225)  =  2.25 joules