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Need some physics help badly T_T

TecHNooB

TecHNooB

Diamond Member
Ok ok... how bout explaining this question. Btw, what's really been bafflin me about the Energy principle is when something is positive and when something is negative. I thought I had it down, but theres negs just like to pop outta nowhere 🙁

Updated with another question:

1. You pull straight up on the string of a yo-yo with a force 0.30 N, and while your hand is moving up a distance 0.16 m, the yo-yo moves down a distance 0.27 m. The mass of the yo-yo is 0.061 kg, and it was initially moving downward with speed 2.6 m/s.

(a) What is the increase in the translational kinetic energy of the yo-yo?

(b) What is the new speed of the yo-yo?

(c) What is the increase in the rotational kinetic energy of the yo-yo?

2. A spring-like device
A certain spring-like device with uneven windings has the property that to stretch it an amount s from its relaxed length requires a force that is given by F = bs3. You suspend this device vertically, and its unstretched length is 15 cm.

(a) You hold the 12 gram mass and throw it downward, releasing it when the length of the spring-like device is 24 cm and the speed of the mass is 3 m/s. Three milliseconds later (10-3 s), what is the stretch of the device, and what is the speed of the mass?

 
don't ask smack Down...

This isn't supposed to be for homework, but if you post the actuall questions some people might actually be nice and help you.
 
Ok, updated with question. I need a good thorough explanation not just the answer =] Thnx smart ATers!
 
umm, well im gonna go get dinner, but those are pretty straightforward, hopefully someone else can answer those pretty quickly 😛.
 
For question 1:

What are the physical dimensions of the yo-yo? Can't solve the problem without knowing its moment of inertia.

Also, what kind of weight is the string and friction from the string to the yo, along with is the yo tied around a spool (in the middle of the yo) or does the string go through a hole on the spool?

For question 2:

m((dx)^2)/((dt)^2)+rm(dx/dt)+3(m/s)+s(x)+24cm=0

There is your differential equation. I was going to solve for everything but you don't have a damping effect and I felt that was unrealistic.

I guess you can also assume your x(t)=A*e^(gamma*t).

What is b? I'm assuming bs3 means b * s^3.
 
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