Suppose that an arrow was fired vertically upward from a crossbow at ground level and that it struck the ground 20 seconds later. If air resistance may be negl

Question

can anyone help solve this math word problem.

Answer 1

Part of the question was cut off.  But we have sufficient information to compute the initial upward velocity.  Using feet, ft/s, and g = 32 ft/s², the equation of motion is

 

h(t) = -(1/2)gt² + v₀t 

 

h(t) = -16t² + v₀t

 

h(20) = 0 = -16(20)² +20v₀

 

v₀ = 320 ft/s

 

What is the rest of the problem?

Answer 2

Or you can reason your way through the problem instead of using a formula. Let g be -10 m/s^2. 

We are told no air resistance so the time it takes the arrow to reach its peak is equal to the time it takes to fall from its peak. Thus, it takes 10 s to reach its peak. What is the velocity of the arrow at its peak? Think about this and you can calculate the initial velocity in your head.