Question

If a car of mass 1200kg is moving along a highway at 120 km/h, what is the car’s kinetic energy as determined by someone standing alongside the highway?

Short answer

The car’s kinetic energy (K.E) as determined by someone standing alongside the highway is$6.67\times {10}^5\mathrm{J}$

Step-by-step solution

Given information

It is given that,

1. Mass of the car is m=1200kg
2. Velocity of the car is v =120 km/h

Determining the concept

The problem deals with the kinetic energy of an object. It is the energy that an object has due to its motion. Find the car’s kinetic energy (K.E) as determined by someone standing alongside the highway by putting the mass and velocity of the car in the corresponding formula.

Formula:

Kinetic energy is given by,

$\mathrm{K}.\mathrm{E}.=\frac{1}{2}m{v}^{\mathit{2}}$

Where,

m is the mass and v is the velocity.

Determining the car’s kinetic energy (K.E) as determined by someone standing alongside the highway

The velocity of the car is,

$$\begin{gathered} v=120\frac{\mathrm{km}}{h}\times \frac{5}{18} \\ =33.33\mathrm{m}/\mathrm{s} \end{gathered}$$

The kinetic energy of the car is,

role="math" localid="1657882920517" $$\begin{gathered} \mathrm{K}.\mathrm{E}.=\frac{1}{2}{\mathrm{mv}}^2 \\ \mathrm{K}.\mathrm{E}.=\frac{1}{2}\left(1200\right){\left(33.33\right)}^2 \\ \mathrm{K}.\mathrm{E}.=6.67\times {10}^5\mathrm{J} \end{gathered}$$

Therefore, the car’s kinetic energy (K.E) as determined by someone standing alongside the highway is $6.67\times {10}^5\mathrm{J}$.