# Homework Help: Radial Acceleration on a string

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1. Sep 15, 2018

### alexi_b

1. The problem statement, all variables and given/known data
A ball on the end of a string is whirled around in a horizontal circle of radius 0.250m. The plane of the circle is 1.06m above the ground. The string breaks and the ball lands 1.90m (horizontally) away from the point on the ground directly beneath the ball's location when the string breaks. Calculate the radial acceleration of the ball during its circular motion.

2. Relevant equations
Ar = -Ac = v^2/r

3. The attempt at a solution
I see no relevance between the last two measurements and only the radius is of use, but obviously they come into play somehow. I don't know where to begin with this so any help would be appreciated!!

2. Sep 16, 2018 at 1:01 AM

### Delta²

Use projectile motion equations for after the string breaks with $v_0=v$ and $\theta=0$, where $v$ the tangential velocity the moment the string breaks
You should be able to calculate $v_0$ using projectile motion equations and the data given by the problem. Then you just plug this $v_0=v$ into the equation you have wrote in part 2. Relevant equations.

Last edited: Sep 16, 2018 at 1:14 AM
3. Sep 16, 2018 at 8:01 AM

### alexi_b

If theta is equal to zero won’t the whole top part of the equation be 0 as well? And then would mean I couldn’t solve for the Vo

4. Sep 16, 2018 at 8:34 AM

### Delta²

if theta is 0, that only means that $V_{0y}=0$ and $V_{0x}=V_0\cos0=V_0$

5. Sep 16, 2018 at 8:37 AM

### alexi_b

I’m still confused, where is the cos coming in from?