Finding Lee's mass when she jumps off a skateboard

[Kate2018]

Homework Statement

Lee is riding on her 6 kg skateboard with a constant speed of 2 m/s. She jumps off of her skateboard and continues forward with a velocity of 4 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 18.5 m/s relative to the ground. What is Lee’s mass?

Homework Equations

m1v1+m2v2= (m1+m2)v3
m1v1+m2v2=m1v3+m2v4

The Attempt at a Solution

Info
m1=?
v1= 2m/s
m2= 6kg
v2=2m/s
v3=4m/s
v4= 18.5m/s

 

[berkeman]

Homework Statement

Lee is riding on her 6 kg skateboard with a constant speed of 2 m/s. She jumps off of her skateboard and continues forward with a velocity of 4 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 18.5 m/s relative to the ground. What is Lee’s mass?

Homework Equations

m1v1+m2v2= (m1+m2)v3
m1v1+m2v2=m1v3+m2v4

The Attempt at a Solution

Info
m1=?
v1= 2m/s
m2= 6kg
v2=2m/s
v3=4m/s
v4= 18.5m/s

So the skateboarder jumps off faster forward and the skateboard goes forward faster too. That would be a great way to create free energy... I guess I'm missing something...

 

[Abhishek kumar]

So the skateboarder jumps off faster forward and the skateboard goes forward faster too. That would be a great way to create free energy... I guess I'm missing something...

Homework Statement

Lee is riding on her 6 kg skateboard with a constant speed of 2 m/s. She jumps off of her skateboard and continues forward with a velocity of 4 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 18.5 m/s relative to the ground. What is Lee’s mass?

Homework Equations

m1v1+m2v2= (m1+m2)v3
m1v1+m2v2=m1v3+m2v4

The Attempt at a Solution

Info
m1=?
v1= 2m/s
m2= 6kg
v2=2m/s
v3=4m/s
v4= 18.5m/s

Go and check your problem details again something is missing i guess.

 

[PeroK]

Homework Statement

Lee is riding on her 6 kg skateboard with a constant speed of 2 m/s. She jumps off of her skateboard and continues forward with a velocity of 4 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 18.5 m/s relative to the ground. What is Lee’s mass?

Homework Equations

m1v1+m2v2= (m1+m2)v3
m1v1+m2v2=m1v3+m2v4

The Attempt at a Solution

Info
m1=?
v1= 2m/s
m2= 6kg
v2=2m/s
v3=4m/s
v4= 18.5m/s

I suspect the skateboard is supposed to go flying backwards.

That said, this is a poor question. You have to assume that there is no friction possible between the skateboard and the ground. In general, when you jump the Earth is involved. So, it's not good to develop the idea that conservation of momentum applies to jumping.