Momentum of child running problem

[quickclick330]

Momentum...please help!

Homework Statement

A child of mass 31 kg sits on a wooden horse on a carousel. The wooden horse is 4.2 m from the center of the carousel, which rotates at a constant rate and completes one revolution every 6.7 seconds.

What are the magnitude and direction of the perpendicular component of dp/dt for the child

Homework Equations

p = mv

The Attempt at a Solution

speed = d/t = 3.9 m/s
p = mv = 31 kg*3.9 m/s = 12.09 kg*m/s

But I don't know how to compute the components of dp/dt? I know the parallel component is 0 and has no direction, so what would the perpendicular one be? Thanks for the help!

 

[Astronuc]

Well, dp/dt is a force.

Think of the centripetal/centrifugal forces.

 

[quickclick330]

so is it essentially the components of the centripetal force?

 

[Astronuc]

Essentially that.

The acceleration comes from the change of the direction of velocity rather than change of the tangential speed. dp/dt = m dv/dt where m is the constant mass, and the speed of v is constant, but the vector changes direction constantly.

The horse holds the child, who would otherwise fly off the merrygoround tangentially. The horse and child are in static equilibrium - the child's mass imposes a force on the horse which imposes an equal force back on the child holding him or her in place.

http://hyperphysics.phy-astr.gsu.edu/hbase/circ.html

 

[quickclick330]

so dp/dt = m *dv/t = 31 kg * 3.9 m/s / 6.7 s = 18.03 kg*m/s/s. how do I get the components out of this?

 

[quickclick330]

nevermind...i finally got it :-) thanks!