Question

ILI

I
IN
A 600 kg car is at rest, and then accelerates to 5 m/s.
What is its original kinetic energy? J
What is its final kinetic energy? J
How much work was used?
1. 0
2. 7,500
3. 7,500

Answer 1

1) Original kinetic energy: 0

The kinetic energy of an object is given by:

where m is the mass of the object and v the speed of the object.

In this problem, the mass of the car is m=600 kg, but its initial speed is zero (it is at rest), so v=0 and Ki=0.

2) Final kinetic energy: 7,500 J

Using again the formula for the kinetic energy:

And using the mass of the car (m=600 kg) and its final speed (v=5 m/s), we find

3) Work used: 7,500 J

The kinetic energy theorem states that the work done on an object is equal to its gain in kinetic energy:

Using the kinetic energies found in the previous points, we find the work done

:

Answer 2

The original kinetic energy will be 0 J and the final kinetic energy will be 7500 J and the amount of work utilized will be similar to the final kinetic energy i.e., 7500 J.

Step-by-step explanation:

As it is known that the kinetic energy is defined as the energy exhibited by the moving objects. So the kinetic energy is equal to the product of mass and square of the velocity attained by the car. Thus,

`\text {Kinetic energy}=(1)/(2) m v^(2)`

So the initial kinetic energy will be the energy exerted by the car at the initial state when the initial velocity is zero. Thus the initial kinetic energy will be zero.

The final kinetic energy is

`\text {Kinetic energy}=(1)/(2) m v^(2)=(1)/(2) * 600 * 5 * 5` = 7500 J

As the work done is the energy required to start the car from zero velocity to 5 m/s velocity.

Work done = Final Kinetic energy - Initial Kinetic energy

Thus the work utilized for moving the car is

Work done = 7500 J - 0 J = 7500 J

Thus, the initial kinetic energy of the car is zero, the final kinetic energy is 7500 J and the work utilized by the car is also 7500 J.