Salmon often jump waterfalls to reach their breeding grounds. starting 3.16 m from a waterfall 0.379 m in height, at what minimum speed must a salmon jumping at an angle of 37.6 ◦ leave the water to continue upstream? the acceleration due to gravity is 9.81 m/s 2 . answer in units of m/s.

The problem corresponds to the motion of a projectile (the salmon), with initial speed , initial direction and vertical acceleration downward. The two equations which gives the horizontal and vertical position of the salmon at time t are

(1)

(2)

We can solve the problem by requiring Sx=3.16 m and Sy=0.379 m, the data of the problem.

Solving eq.(1) for t:

And substituting this expression of t into eq.(2), we get the following expression for :

And substituting the numbers into the equation, we find

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.