Question

two kids are rollerskating. amy, with a mass of 55 kg, is traveling forward at 3 m/s. jenny, who has a mass of 40 kg, is traveling in the opposite direction at 5 m/s. they crash into each other and hold onto each other so that they move as one mass. how fast are they traveling?

Answer 1

The momentum of a system is going to be equal before and after they crashed

The formula for momentum is mass * velocity

so conservation of momentum

\( m_1v_1 + m_2v_2 = (m_1+m_2)v\)

so we know the first kid
her mass \( m_1\) is 55 kg
and her speed is 3 m/s

the second kid has a mass \( m_2\) of 40 kg
and her speed is -5 m/s
it's NEGATIVE because it's in the opposite direction

can you plug that into the formula and solve for \( v\)

Answer 2

im thinking the answer might be 0.368 m/s

Answer 3

That's almost correct, but in which direction is she going?

Answer 4

negative, so -0.368 m/s? bcs its the direction jenny was traveling??

Answer 5

yes, it's negative because we defined the direction Jenny was going as negative

Answer 6

Good job! :)

Answer 7

oky thank you :)

Answer 8

No problem :))