|May4-06, 06:42 PM||#1|
A 50 kg boy runs at a speed of 10 m/s and jumps onto a cart. The cart is initially at rest. If the speed of the cart with the boy on it is 2.50 m/s, what is the mass of the cart?
I don't know what to do. This probelem seems very simple but I don't know where to start.
These I know are the knowns:
vo(cart) = 0 m/s
vf(cart) = 2.50 m/s
vo(boy) = 10 m/s
vf(boy) = 2.5 m/s
So I know velocities and I know the mass of the boy.
Should I start off by finding the acceleration from F=ma, since I know a mass? But then I don't know how to find F. I know Fn = mg in the y component, but I don't know what I would use Fn next for. Am I supposed to use kinematics equations? But I don't know a, x, or time. Direction is needed, thanks!!
|May4-06, 06:46 PM||#2|
It's much simpler than you think. Hint: What's conserved when the boy "collides" with the cart?
|May4-06, 06:55 PM||#3|
Sum of external forces = 0! thank you!!!
|May5-06, 02:08 PM||#4|
SO yeah, the net force is zero. This clue leads us to what principle pf physics, ya know, with its own set of silly equations and all.
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