High School

A 9 kg mass traveling at a speed of 13 m/s strikes a stationary 9 kg mass head-on, and the two masses stick together.

(a) What was the initial total kinetic energy?

A. 1521 J
B. 169 J
C. 219 J
D. 338 J

Answer :

Final answer:

The initial total kinetic energy of a 9 kg mass traveling at 13 m/s that strikes a stationary 9 kg mass is calculated using the formula KE = 1/2 mv^2 and then doubling the result for the two masses, leading to an answer of 1521 J.

Explanation:

Kinetic energy is the energy of motion, observable as the movement of an object or subatomic particle. Every moving object and particle have kinetic energy. A person walking, a soaring baseball, a crumb falling from a table and a charged particle in an electric field are all examples of kinetic energy at work.

To calculate the initial total kinetic energy of the system, we use the formula KE = ½ mv², where m is the mass and v is the velocity. Since we know the mass of the moving object is 9 kg and the velocity is 13 m/s, we can plug these values into the formula: KE = ½ (9 kg)(13 m/s)² = ½ (9 kg)(169 m²/s²) = ½ * 9 * 169 J = 4.5 * 169 J = 761.5 J.

However, because there are two identical masses involved, we double the kinetic energy of the single moving mass to account for the total system, which gives us a total initial kinetic energy of 1521 J. Therefore, the correct answer is a) 1521 J.