An artillery shell is launched on a flat, horizontal field at α = 31.4° with respect to the horizontal and with v0 = 269 m/s. A) What is the horizontal distance covered by the shell after 4.88 s of flight? B) What is the height of the shell at this moment? Answer: 567m
I understand question A, but not B.
I've used these equations:
viy = visinα = (269)(sin31.4) = 140.15
yf = yi + viy∆t + ½a∆t^2 ⇒ yf = viy∆t + ½g∆t^2, yi = 0
yf = (140.15)(4.88) + ½(9.8)(4.88)^2 = 800.62m, but this isn't right.
If you do:
yf = (140.15)(4.88) - ½(9.8)(4.88)^2 (minus instead of add)
yf = 567.24m, this is the correct answer.
Why do you do - instead of +?
I understand question A, but not B.
I've used these equations:
viy = visinα = (269)(sin31.4) = 140.15
yf = yi + viy∆t + ½a∆t^2 ⇒ yf = viy∆t + ½g∆t^2, yi = 0
yf = (140.15)(4.88) + ½(9.8)(4.88)^2 = 800.62m, but this isn't right.
If you do:
yf = (140.15)(4.88) - ½(9.8)(4.88)^2 (minus instead of add)
yf = 567.24m, this is the correct answer.
Why do you do - instead of +?