Question

Question in picture.

Answer 1

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:

$KE=\frac{1}{2}mv^{2}$

Where:

$KE=KineticEnergy\\m=mass\\v=velocity$

So,

First object, (going to the right):

$m=7.20kg\\v=2\frac{m}{s}$

$KE_{1}=\frac{1}{2}*7.20Kg*(2\frac{m}{s})^{2}=14.4Joules$

Second object:, (going to the left):

$m=5.75kg\\v=-1.30\frac{m}{s}$

$KE_{2}=\frac{1}{2}*5.75kg*(-1.30\frac{m}{s})^{2}=4.86Joules$

Remember,

$1Joule=1Kg.\frac{m^{2}}{s^{2} }$

Hence,

The total kinetic energy after the collision will be:

$T=KE_{1}+KE_{2}=14.4Joules+4.86joules=19.26joules=19.3joules$

The total kinetic energy after the collision is 19.3 joules (rounded to the nearest tenth)

Have a nice day!