Find the mass of the skateboard

[Maiia]

Homework Statement

A 43.9 kg student runs down the sidewalk and jumps with a horizontal speed of 4.03 m/s onto a stationary skateboard. The student and skateboard move down the sidewalk with a speed of 3.85 m/s.
a) find the mass of the skateboard. answer in units of kg
b) How fast would the student have to jump to have a final speed of 6.93 m/s. Answer in units of m/s.

I assume I would need to find how fast he runs down the sidewalk to begin? Would I then add that to the horizontal speed, or would I have to add them like vectors...?

 

[Dick]

How would you figure that out? I don't think you can. Just assume the students speed when landing on the skateboard is 4.03m/s and use conservation of momentum.

 

[Maiia]

i see. Thank you for your help! :)