Question

A 60kg student traveling in a 1000kg car with a constant velocity has a kinetic energy of 1.2 x 10^4 J. What is the speedometer reading of the car in km/hr?

Answer 1

17.64 km/h

Step-by-step explanation:

mass of car, m = 1000 kg

Kinetic energy of car, K = 1.2 x 10^4 J

Let the speed of car is v.

Use the formula for kinetic energy.

`K = (1)/(2)mv^(2)`

By substituting the values

`1.2* 10^(4) = (1)/(2)* 1000* v^(2)`

v = 4.9 m/s

Now convert metre per second into km / h

We know that

1 km = 1000 m

1 h = 3600 second

So,
`v = \left ((4.9)/(1000)   \right )* \left ( (3600)/(1) \right )`

v = 17.64 km/h

Thus, the reading of speedometer is 17.64 km/h.