# Find the minimum speed

Tags:
1. Nov 25, 2014

### HaLAA

1. The problem statement, all variables and given/known data
You've taken a summer job at a water park. In one stunt, a water skier is going to glide up the 2.0-m-high frictionless ramp shown, then sail over a 5.0-m-wide tank filled with hungry sharks. You will be driving the boat that pulls her to the ramp. She'll drop the tow rope at the base of the ramp just as you veer away.
What minimum speed must you have as you reach the ramp in order for her to live to do this again tomorrow?
2. Relevant equations
U=mgh, K=0.5mv^2, W=Fd

3. The attempt at a solution
when the water skier is standing on the ramp, there is only gravitational potential energy
Ei=U=m*2m*g
then, when I am pull the water skier, there are kinetic energy and work by pulling the water skier
Ef=K+W=0.5mv^2+5F, F=mg because the skier is skiing on water

thus, Ei+Ef= m*g*2=0.5mv^2+5mg= g(h-d)=0.5v^2

I get v=7.7m/s

I am not sure this is the right answer or not.

2. Nov 25, 2014

### Simon Bridge

I don't follow your reasoning - how did you work out the energy needed to get over the 5m distance?

3. Nov 26, 2014

### HaLAA

while the skier is sailing on water, I think the work on water just equal to mgd.

4. Nov 26, 2014

### Simon Bridge

Why?
And what has that got to do with jumping the shark tank?
You are asked for the speed at the bottom of the ramp right?