Homework Help

A 39 kg child stands at rest on ice skates. She catches a 1.0 kg ball moving...

user profile pic

heyitsmegxx | Student, Undergraduate | eNoter

Posted March 29, 2012 at 9:22 PM via web

dislike 0 like

A 39 kg child stands at rest on ice skates. She catches a 1.0 kg ball moving horizontally at 9.5 m/s. What is her speed after she's caught the ball?

2 Answers | Add Yours

user profile pic

ksy1995 | Student, Grade 10 | eNoter

Posted March 29, 2012 at 9:35 PM (Answer #1)

dislike 0 like

39(0)+1(9.5)=(39+1)v

9.5=40v

v=9.5/40

  =0.2375m/s

 

user profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted March 29, 2012 at 10:06 PM (Answer #2)

dislike 0 like

A child with a mass of 39 kg stands at rest on ice skates. She catches a 1.0 kg ball moving horizontally at 9.5 m/s.

Let the speed of the child after the ball has been caught be s. The law of conservation of momentum states that the total momentum in the system is a constant. The total momentum initially is equal to the total final momentum.

Initially the total momentum of the ball and the girl is 1*9.5 + 39*0 = 9.5. The total final momentum is (39+1)*s

This gives 40s = 9.5

=> s = 9.5/40 = 0.2375 m/s

The speed of the girl after the she catches the ball is 0.2375 m/s.

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes