physics kinematics question please?

Question

A rock climber throws a small first aid kit to another climber who is higher up the mountain. The initial velocity of the kit is 21 m/s at an angle of 55° above the horizontal. At the instant when the kit is caught, it is traveling horizontally, so its vertical speed is zero. What is the vertical height between the two climbers?

Answer 1

This is calculated using
vy(t)=vy0-g*t
when vy(t)=0, it satisfies the condition

so
0=21*sin(55)-10*t
solve for t and plug into
y(t)=21*sin(55)*t-5*t^2

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