Select the correct answer.

Objects [tex]A[/tex] and [tex]B[/tex] each have a mass of 25 kilograms. Object [tex]A[/tex] has a velocity of 5.98 meters/second. Object [tex]B[/tex] is stationary. They undergo a perfectly elastic collision in one dimension. What is the total kinetic energy of the system after the collision?

A. [tex]1.2 \times 10^2[/tex] joules
B. [tex]4.5 \times 10^2[/tex] joules
C. [tex]5.0 \times 10^2[/tex] joules
D. [tex]9.5 \times 10^2[/tex] joules
E. [tex]1.1 \times 10^3[/tex] joules



Answer :

To determine the total kinetic energy of the system after the collision, we need to follow these steps:

1. Calculate the kinetic energy of object [tex]\( A \)[/tex] before the collision.
The kinetic energy ([tex]\( KE \)[/tex]) of an object is given by the formula:
[tex]\[ KE = \frac{1}{2} m v^2 \][/tex]
where [tex]\( m \)[/tex] is the mass and [tex]\( v \)[/tex] is the velocity.

For object [tex]\( A \)[/tex]:
[tex]\[ m_A = 25 \text{ kg}, \quad v_A = 5.98 \text{ m/s} \][/tex]
[tex]\[ KE_A = \frac{1}{2} \times 25 \times (5.98)^2 \][/tex]
The result is approximately 447.005 joules.

2. Calculate the kinetic energy of object [tex]\( B \)[/tex] before the collision.
Since object [tex]\( B \)[/tex] is stationary, it has no kinetic energy.
[tex]\[ m_B = 25 \text{ kg}, \quad v_B = 0 \text{ m/s} \][/tex]
[tex]\[ KE_B = \frac{1}{2} \times 25 \text{ kg} \times (0)^2 = 0 \text{ joules} \][/tex]

3. Determine the total kinetic energy before the collision.
[tex]\[ KE_{\text{total before}} = KE_A + KE_B = 447.005 \text{ joules} + 0 \text{ joules} = 447.005 \text{ joules} \][/tex]

4. Use conservation of kinetic energy for a perfectly elastic collision.
In a perfectly elastic collision, the total kinetic energy before the collision is equal to the total kinetic energy after the collision.
[tex]\[ KE_{\text{total after}} = KE_{\text{total before}} = 447.005 \text{ joules} \][/tex]

Given the above steps, the total kinetic energy of the system after the collision is approximately:
[tex]\[ 447.005 \text{ joules} \][/tex]

Comparing this result with the provided options, the closest match is:
[tex]\[ B. 4.5 \times 10^2 \text{ joules} \][/tex]

So, the correct answer is:
[tex]\[ \boxed{B} \][/tex]