Hello!
The answer is: A. 19.3 joules
Why?
Since it's an elastic collision, the kinetic energy after and before the collision will be the same.
Kinetic energy can be calculated using the following equation:
[tex]KE=\frac{1}{2}mv^{2}[/tex]
Where:
[tex]KE=KineticEnergy\\m=mass\\v=velocity[/tex]
So,
First object, (going to the right):
[tex]m=7.20kg\\v=2\frac{m}{s}[/tex]
[tex]KE_{1}=\frac{1}{2}*7.20Kg*(2\frac{m}{s})^{2}=14.4Joules[/tex]
Second object:, (going to the left):
[tex]m=5.75kg\\v=-1.30\frac{m}{s}[/tex]
[tex]KE_{2}=\frac{1}{2}*5.75kg*(-1.30\frac{m}{s})^{2}=4.86Joules[/tex]
Remember,
[tex]1Joule=1Kg.\frac{m^{2}}{s^{2} }[/tex]
Hence,
The total kinetic energy after the collision will be:
[tex]T=KE_{1}+KE_{2}=14.4Joules+4.86joules=19.26joules=19.3joules[/tex]
The total kinetic energy after the collision is 19.3 joules (rounded to the nearest tenth)
Have a nice day!
