a 60-kg student travelling in a car with a constant velocity has a kinetic energy of 1.2 *10^4 J. What is the speedometer reading of the car in km/h?

Why don't you just ask the car? It should be pretty good at reading its own speedometer!

To find the speedometer reading of the car, we can use the formula for kinetic energy:

Kinetic energy (KE) = (1/2) * mass * velocity^2

Given:
Mass of the student (m) = 60 kg
Kinetic energy (KE) = 1.2 * 10^4 J

We need to find the velocity (v) in m/s, and then convert it to km/h.

Rearranging the formula for kinetic energy:
KE = (1/2) * m * v^2
1.2 * 10^4 = (1/2) * 60 * v^2
v^2 = (2 * 1.2 * 10^4) / 60
v^2 = 240 / 60
v^2 = 4

Taking the square root of both sides, we find:
v = √(4)
v = 2 m/s

Now, let's convert the velocity from m/s to km/h.

1 m/s is equal to 3.6 km/h, so we can multiply the velocity by 3.6 to get the speed in km/h.

v (km/h) = v (m/s) * 3.6
v (km/h) = 2 * 3.6
v (km/h) = 7.2 km/h

Therefore, the speedometer reading of the car is 7.2 km/h.

To determine the speedometer reading of the car in km/h, we can use the equation for kinetic energy:

Kinetic Energy = 1/2 * mass * velocity^2

Given information:
Mass (m) = 60 kg
Kinetic Energy (KE) = 1.2 * 10^4 J

The equation can be rearranged to solve for velocity:

Velocity^2 = (2 * KE) / mass

Let's plug in the values:

Velocity^2 = (2 * 1.2 * 10^4 J) / 60 kg
Velocity^2 = 2400 J / 60 kg
Velocity^2 = 40 m^2/s^2

To find the velocity, we take the square root:

Velocity = √(40 m^2/s^2)
Velocity ≈ 6.32 m/s

Now we need to convert the velocity from m/s to km/h:

1 km = 1000 m
1 hour = 3600 seconds

Speed in km/h = (velocity in m/s * 1 km/1000 m * 3600 s/1 hour)

Speed in km/h = (6.32 m/s * 1 km/1000 m * 3600 s/1 hour)
Speed in km/h ≈ 22.8 km/h

Therefore, the speedometer reading of the car would be approximately 22.8 km/h.

(1/2)(60) v^2 = 12,000 Joules

v = 20 meters/second

20 *3.6 = 8.2 km/h