Need help finding velocity

  • #1
The question I'm having trouble with is:
A child of mass 28.0 kg is sliding on ice with a velocity of 2.25 m/s in the positive x direction. She is holding a 2.4 kg ball in her hand. She throws the ball straight ahead of her with a velocity of 2.70 m/s (in the x direction). What is her velocity immediately after releasing the ball?

I think I need to get the rotational inertia for the ball to get its kinetic energy but i'm not given a radius.
 

Answers and Replies

  • #2
Doc Al
Mentor
45,140
1,443
I think I need to get the rotational inertia for the ball to get its kinetic energy but i'm not given a radius.
You won't need rotational inertia. (No reason to think rotation is involved here.)

Instead, what physical principles might be relevant? Is anything conserved as she throws the ball?
 
  • #3
998
15
I think that if the mass is not given you are expected to consider only the translational K.E.

Think about momentum!
 

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