Physics 11: Calculate Velocity of Student Throwing Backpack on Ice Surface

[roxxyroxx]

Homework Statement

A 55 kg student wearing skates stands at rest on a frictionless horizontal ice surface. She throws a 10 kg backpack horizontally with a speed8.3 m/s .
What is the velocity of the student after she throws the backpack?

Homework Equations

F\Deltat = m\Deltav

The Attempt at a Solution

so the answer should be 1.5 m/s [N] and i got this by dividing 10 kg (backpack) by 55 kg (student) and then multiplying that answer by 8.3 m/s . is this the right way or is there a proper formula i should follow?
thanks !

 

[Doc Al]

That's correct. The impulse given to the backpack will be exactly equal and opposite to the impulse given to the student. Thus:
m_student*v_student = m_backpack*v_backpack

Just solve for v_student.

 

[roxxyroxx]

great, thanks !