# Homework Help: Velocity in a circular path

1. Mar 30, 2012

### mccarthyp64

1. All in the picture

2.v2=u2+2as

3. I have no idea where to start, I went through all the equations but i dont have time or velocity to sub in :(

It also has circular motion which may or may not introduce pi. I didn't think this would be relevant but anyway.

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2. Mar 30, 2012

### Staff: Mentor

The question concerns energy and energy conservation. What forms of energy can you identify in the scenario?

3. Mar 30, 2012

### mccarthyp64

There is kinetic and potential gravitational energy
so Ek=1/2mv2 but that needs velocity so:
Ep=mgh but that only gives horizontal velocity whereas, I need all velocity.

4. Mar 30, 2012

### Staff: Mentor

Why do you need velocity? What will velocity tell you?

Why do you suppose that the height of the object only reaches 0.14 m after it breaks the pencil rather than returning to its starting height of 0.30 m? What has changed?

5. Mar 30, 2012

### mccarthyp64

for q 25 velocity is the answer
and in 26 I need the work done

6. Mar 30, 2012

### Staff: Mentor

Both questions involve changes in energy. Consider the energy changes taking place.

7. Mar 30, 2012

### mccarthyp64

Ep=mgh=Ek=1/2mv2
1.176=0.4*9.8*0.3=1.176=0.5(0.4)(v)2
(1.176/0.5)/0.4=v2=5.88
√(5.88)=2.42=ANS!!!!
YAY thanks gneill :)