- #1

RJWills

- 16

- 0

## Homework Statement

F=Force, v=Velocity, a=acceleration m=mass (0.01kg) R=Normal Reaction to surface

Hi, can anyone help, I keep getting the wrong answer on this question and it is really annoying me. Here is a picture of the diagram:

"A Marble of mass 0.01kg is on top of a smooth hemispherical bowl and given an initial speed of 1 m/s. The bowl has a radius of 0.5m and centre o.

a) The marble descends 0.1m, find the speed.

**got this part correct and figured out that v^2=1+0.2g**

b) "Find the normal reaction of the bowl at this point"

## Homework Equations

I have a solution for Velocity^2=1+0.2g

## The Attempt at a Solution

So I have v^2=1+0.2g, now trying to resolve in the direction of R using F=ma I got:

R-0.01gcos(alpha)=m x (v^2/r)

=>R=0.01x(1+0.2g/0.5)

Now, trying to find alpha I thought of the height raise as 0.4m and the radius 0.5 to create a right angled triangle, getting cos(alpha)=0.4/0.5, and subsequently alpha to equal 36.86... deg.

When I sub this is my value that I get for R=0.1376, however in the book it says it should = 0.0192.

I have tried re doing it from scratch twice, faffing about with different bits and I just cannot get it right :/