# Kinetic Energy Formula

The Kinetic energy is the energy that an object has due to its motion. *E _{k}*, is the energy of a mass,

*m*, in motion,

*v*.

^{2}*E _{k} = 1/2 mv^{2} *

*E _{k}* = Kinetic energy

*m* = mass

*v* = velocity

Kinetic Energy Formula Questions.

1) The mass of a baby elephant is 113 kg, and it walks at a constant velocity of 0.5 m/sec. What is the kinetic energy for the baby elephant?

Answer: The mass, *m* = 113 kg, and the velocity, *v* = 0.5 m/sec. Use the kinetic energy equation.

*E _{k} = 1/2 mv^{2} *

*E _{k}* = 1/2 (113 kg) (0.5 m/sec)

^{2}

*E _{k}* = 1/2 (113 kg)(0.25 m

^{2}/s

^{2})

*E _{k}* = 14.125 kg m

^{2}/sec

^{2}= 14.125 Joules

[2] If the kinetic energy of a car is 320,000 Joules (3.2 x 10^{5} J), and it's velocity is 25 m/s, what is the vehicle's mass?

Answer: The kinetic energy for the car in motion is *E _{k}* = 320,000 J = 32,000 kg m

^{2}/s

^{2}. The velocity of the car,

*v*= 25 m/s.

*E _{k} = 1/2 mv^{2}*

*E _{k}/0.5v^{2}* = m

*m* = (320,000 kg m^{2}/s^{2})/[0.5(25 m/s)^{2}]

*m* = (320,000 kg m^{2}/s^{2}/[(0.5)(625)m^{2}/s^{2}]

*m* = (320,000 kg m^{2}/s^{2}/312.5 m^{2}/s^{2}

*m* = 1024 kg

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