Answer: 244.05 J
Explanation:
To find speed at 30 m above the ground use equation:
V²=Vo²-2Gs
V0=31.4m/s
s=30m
G=9.81m/s²
-----------------------
V²=31.4²-2*9.81*30
V²=985.96+588.6
V²=1574.56
V=39.68m/s ---speed of arrow on 30 m obove the ground
Use equation for kinetic enrgy:
Ke=mV²/2
m=0.155kg
V=39.68m/s
-------------------------
Ke=0.155kg*(39.68m/s)²/2
Ke=0.155*1574.5/2
Ke=244.05J
