Answer:
The speed of the Dan is 38.33 m/s.
Explanation:
Given that,
Mass of Dan, m = 60 kg
Mass of skateboard, m' = 5 kg
Initial speed of Dan and skateboard is, u = 4 m/s
He suddenly jumps backward off the skateboard. The skateboard kicks forward at a speed of 6 m/s, v' = 6 m/s
We need to find the speed of Dan as his feet hit the ground. In the whole process, the momentum remains conserved. Let v is the speed of Dan. Using conservation of linear momentum as :
[tex](m+m')u=mv+m'v'[/tex]
[tex](60+5)\times 4=60v+5\times 6\\\\260=60v+30\\\\v=38.33\ m/s[/tex]
So, the speed of the Dan is 38.33 m/s.