Question

predicting changes in kinetic energy quick check
which object has the greatest kinetic energy? (1 point)
○ a yellow car with a mass of 500 kg moving at 12 m/s
○ a green car with a mass of 500kg moving at 21 m/s
○ a blue car with a mass of 500 kg moving at 30 m/s
○ a red car mass of 500 kg moving at 3 m/s

Explanation:

Step1: Recall the formula for kinetic energy

The formula for kinetic energy is \(KE=\frac{1}{2}mv^{2}\), where \(m\) is the mass and \(v\) is the velocity.

Step2: Calculate the kinetic energy for each car

• For the yellow car: \(m = 500\space kg\), \(v=12\space m/s\).

\(KE_{yellow}=\frac{1}{2}\times500\times12^{2}= \frac{1}{2}\times500\times144 = 36000\space J\)

• For the green car: \(m = 500\space kg\), \(v = 21\space m/s\).

\(KE_{green}=\frac{1}{2}\times500\times21^{2}=\frac{1}{2}\times500\times441= 110250\space J\)

• For the blue car: \(m = 500\space kg\), \(v = 30\space m/s\).

\(KE_{blue}=\frac{1}{2}\times500\times30^{2}=\frac{1}{2}\times500\times900 = 225000\space J\)

• For the red car: \(m = 500\space kg\), \(v = 3\space m/s\).

\(KE_{red}=\frac{1}{2}\times500\times3^{2}=\frac{1}{2}\times500\times9= 2250\space J\)

Answer:

a blue car with a mass of 500 kg moving at 30 m/s