# Radial Acceleration on a string

• alexi_b
In summary: I’m still confused, where is the cos coming in from?The cos comes in from the equation for the tangential velocity.

## Homework Statement

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.

Ar = -Ac = v^2/r

## 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!

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. Homework Equations .

Last edited:
Delta² said:
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. Homework Equations .
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

alexi_b said:
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
if theta is 0, that only means that ##V_{0y}=0## and ##V_{0x}=V_0\cos0=V_0##

Delta² said:
if theta is 0, that only means that ##V_{0y}=0## and ##V_{0x}=V_0\cos0=V_0##
I’m still confused, where is the cos coming in from?