- #1

PsychonautQQ

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- 10

## Homework Statement

a 8kg ball is hanging from a 1.35m string. A 2 kg ball moving horizontally at 5m/s hits the hanging 8kg ball in an elastic collision. What is the tension in the string just after the collision?

## Homework Equations

## The Attempt at a Solution

Initially there is only a gravitational force of 8*9.8 = 78.4 N.

Using conservation of momentum, we can find that the ball has a velocity of 1.25 m/s just after the collision.

so the centripetal acceleration is v^2/r = 1.1574 m/s^2.

That centripetal acceleration is due to a centripetal force point in the opposite direction as the gravitation force

so F_g - M*a_c = answer

78.4 - (8)*(1.1574) =69.14 Newtons

The back of the book says the answer is 102 Newtons.

I feel like I worked this out right as far as my understanding of physics goes, but then I think about it and I feel like the tension should increase.

Even if I add the centripetal force to the gravitational force I come up short of 102 N.

Help?