Calculating Velocity in Circular Motion

[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 don't 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.

 

[gneill]

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 don't 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.

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

 

[mccarthyp64]

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

 

[gneill]

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

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?

 

[mccarthyp64]

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

 

[gneill]

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

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

 

[mccarthyp64]

E_p=mgh=E_k=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 :)