I came across a momentum and kinetic energy question today involving two objects heading towards each other from opposite directions. The object coming from the right, m1, is 250 kg and traveling at 5 m/s. The object from the left, m2, is also 250 kg but traveling at 2 m/s. The text then says the collision is completely inelastic.
I used 0.5(m1v1)^2 + 0.5(m2v2)^2 to find the total kinetic energy before the collision. However, the text I used said this was wrong. It said I should have used -0.5(m2v2)^2 for the kinetic energy of m2 since its velocity, v2, is in the opposite direction of v1.
I thought kinetic energy was scalar and so direction doesn't need to be considered to find the total kinetic energy of the system. Is the text mistaken or am I?
I used 0.5(m1v1)^2 + 0.5(m2v2)^2 to find the total kinetic energy before the collision. However, the text I used said this was wrong. It said I should have used -0.5(m2v2)^2 for the kinetic energy of m2 since its velocity, v2, is in the opposite direction of v1.
I thought kinetic energy was scalar and so direction doesn't need to be considered to find the total kinetic energy of the system. Is the text mistaken or am I?