A thin uniform bar, hanging, is hit by a ball. Find the angular velocity

[Phys121VIU]

Homework Statement

A thin, uniform metal bar, 3m long and weighing 75N, is hanging veritcally from the ceiling by a frictionless pivot. Suddenly it is struck 1.3m below the ceiling by a small 2 kg clay ball, initially traveling horizontally at 14m/s. The ball sticks to the bar

Find the angular velocity of the ball+bar just after the collision.

Homework Equations

The Attempt at a Solution

Angular momentum is conserved so my understanding is that

Angular momentum of the ball = angular momentum of the bar and bar

L_ball = (I_bar + I_ball)ω²

(2kg)(14m/s)(1.3m) = [(1/3)(75N/9.8m/s²)(3m)² + (2kg)(1.3m)²]ω²

so i worked it out and got ω = 1.18 rad/s

but that's not correct...I can't think of any other way to approach it

 

[ehild]

Homework Statement

A thin, uniform metal bar, 3m long and weighing 75N, is hanging veritcally from the ceiling by a frictionless pivot. Suddenly it is struck 1.3m below the ceiling by a small 2 kg clay ball, initially traveling horizontally at 14m/s. The ball sticks to the bar

Find the angular velocity of the ball+bar just after the collision.

Homework Equations

The Attempt at a Solution

Angular momentum is conserved so my understanding is that

Angular momentum of the ball = angular momentum of the bar and bar

L_ball = (I_bar + I_ball)ω²

Are you sure that the last formula is correct?

ehild

 

[Phys121VIU]

Wow..its definitely not squared..thanks:P

Found the answer..1.38rad/s!

 

[ehild]

Well done !