The kinetic energy (KE) of an object can be calculated using the formula:
\[ KE = \frac{1}{2} m v^2 \]
where \( m \) is the mass of the object and \( v \) is its velocity.
Let's calculate the kinetic energy for each car:
-
Blue car:
- Mass = 500 kg
- Velocity = 30 m/s
- \( KE = \frac{1}{2} \times 500 \times (30^2) = \frac{1}{2} \times 500 \times 900 = 225000 \) Joules
-
Green car:
- Mass = 500 kg
- Velocity = 21 m/s
- \( KE = \frac{1}{2} \times 500 \times (21^2) = \frac{1}{2} \times 500 \times 441 = 110250 \) Joules
-
Yellow car:
- Mass = 500 kg
- Velocity = 12 m/s
- \( KE = \frac{1}{2} \times 500 \times (12^2) = \frac{1}{2} \times 500 \times 144 = 36000 \) Joules
-
Red car:
- Mass = 500 kg
- Velocity = 3 m/s
- \( KE = \frac{1}{2} \times 500 \times (3^2) = \frac{1}{2} \times 500 \times 9 = 1125 \) Joules
Now, comparing the kinetic energies:
- Blue car: 225,000 Joules
- Green car: 110,250 Joules
- Yellow car: 36,000 Joules
- Red car: 1,125 Joules
The object with the greatest kinetic energy is the blue car moving at 30 m/s.