A racing car has a mass of 1610 kg. The acceleration of gravity is 9.8 m/s to the second power.What is its kinetic energy if it has a speed of 111 km/h? Answer in units of J.

2 Answers

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

The kinetic energy  K of the car of mass m kilogram with a speed of v metr per second is given by

K =(1/2)mv^2. Given m=1610 kg and velocity  111km/hour = 111000meter/(3600second) = v

K=(1/2)1610*(111000/3600)^2 J

=765309.0278 J

krishna-agrawala's profile pic

krishna-agrawala | College Teacher | (Level 3) Valedictorian

Posted on

Kinetic energy (k) of any moving objects in joules (J) is given by the following formula:

k = (m*v^2)//2


m = mass of the object in kg

v = Speed in m/s


m = 1610 kg

v = 111 km/hours

We can convert speed in km/hrs in speed in m/s by multiplying by 1000/3600. Thus:

v = 111*(1000/3600) = 1110/36 m/s

In this question though the value of acceleration of gravity is given, we do not need it to calculate kinetic energy of the car.

Using the formula for kinetic energy given above we calculate the kinetic energy of car as follows:

k = (m*v^2)//2 = [(1610)*(1110/36)^2}//2 = 765309.0278 J


Kinetic energy of car is 765309.0278 J