# Complex Physics Problem Need Help Please!

1. Jan 13, 2009

### Phillipc

1. The problem statement, all variables and given/known data

A student begins swinging a mass on a string in a horizontal circle. The mass is 1.0 Kg, it starts from rest, the string is 2.0m, the acceleration rate is 2.0 rad/s2, and this is done for 5.0 seconds. Derirmine the final tangential speed of the mass, the angular displacement in revolutions, and the tension force in the string at 5.0s

At 5.0s the string breaks and the mass becomes a projectile. It is released 2.0m above the ground. Determine the final velocity (magnitude and direction) of the mass as it reaches the level of the ground.

Where the projectile reaches the level of the ground there is another identical mass (1.0 Kg) at the top of an inclined plane whose angle is the same as the final angle of the projectile found in part 2 the collision between the masses is inelastic. Determine the final velocity of the 2 masses after the collision.

The masses now slide down the inclined plane to the bottom. The coefficient of friction between the masses and the plane is .05, the length of the incline is 2.0m. Determine the work done by friction while sliding, the initial kinetic energy at the top and the final kinetic energy at the bottom. Determine the net force and acceleration down the incline using the components of weight and the force of friction. Now determine the final velocity using kinematics and verify the final kinetic energy at the bottom.

The masses now begin sliding across a horizontal frictionless surface. They then collide and stick to a spring which is fixed to a wall and begin to oscillate. The value of the spring constant is .1 N/m. determine the amplitude and the angular frequency of the oscillations.

2. Relevant equations
2Pi R
V=-------
T

3. The attempt at a solution

I'm going to be completely honest I have been out of school because of family matters and i dont know where to begin with this problem, any help will be GREATLY APPRECIATED!

Thank You

Phillip M Carreno

Last edited: Jan 13, 2009
2. Jan 14, 2009

### Delphi51

You need some formulas for angular motion.
For steady motion, you have good old d = vt in linear motion and its corresponding formula for angular motion would be $$\theta = \omega t$$
Of course that doesn't apply to this problem because this motion is accelerating.
d = vit + .5at^2 in circular motion would be $$\theta = \omega t + .5 \alpha t^2$$
where omega is the initial angular velocity and alpha is the angular acceleration.
Corresponding to v = vi + at, you would have $$\omega = \omega i + \alpha t$$

Use those formulas to find the final angle and angular velocity.
Translate to linear distance and velocity with $$d = r\theta$$ and $$v = r\omega$$
(that is supposed to be an "r" for radius in the formula, not a greek tau)

See if you can do the first part with all that!

What a lengthy problem - looks like someone is putting you through an obstacle course!

3. Jan 14, 2009

### Phillipc

Yah tell me about it! ok so i've worked it out and i have some answers, if you could perhaps review them i would be forever in your Debt!!

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