Question

a 4lb ball is travelling in a circle radius 3ft speed 6ft/s. the attached cord pulled through the center has constant speed 2ft/s. how much time for the ball to reach 12 ft/s

Answer 1

Step-by-step explanation:

Circle motion

Weight=4lb

Radius=3ft

Velocity Vb= 6ft/s

Velocity Vr=2ft/s

Velocity Vo=12

V2=√Vo²+Vr²

12=√Vo²+2²

Square both side

144=Vo²+4

Vo²=140

Vo=11.83ft/s

Applying conservation of angular momentum

Ha1=Hb2

MbVbr1=MbVor2

r2=Vbr1/Vo

r2=6×3/11.83

r2=1.52ft

The require time is written as.

∆r=Vrt

t=∆r/Vr

t=r1-r2/Vr

t=3-1.52/2

t=0.74sec