Simple problem about relative motion.

VB*sin(45) = -2*sin(45)+10ωYou're calculating VB along the incline, then finding its components. It's been given as 2 m/s, so why calculate it?In summary, a body consisting of two spheres attached by a 10 meter solid long rod is rolling down a 45 degree incline at one end while rolling up a 45 degree incline on the other end. When the connecting rod is horizontal, the sphere rolling down has a velocity of 2 m/s down the incline and an acceleration of 3 m/s^2 down the incline. At this time, the velocity of the sphere rolling up can be calculated using the formula VB = VA+ω
  • #1
ParrotPete
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Homework Statement


A body consisting of two spheres attached by a 10 meter solid long rod is rolling down a 45 degree incline at one end while rolling up a 45 degree incline on the other end.
At the instant when the connecting rod is horizontal the sphere rolling down has the velocity 2 m/s down the incline and the acceleration 3 m/s^2 down the incline. At this time, what is the velocity of the sphere rolling up and what is the angular velocity of the rod?

Homework Equations



VB = VA+ωXrB/A

The Attempt at a Solution


VA=2*(cos(45)*ei-sin(45)*ej
VB = VB*(cos(45)*ei+sin(45)*ej)
rA/B= 10*ei
ω=ω*ez
Doing the calculations
VB cos(45) = cos(45)
VB*sin(45) = -2*sin(45)+10ω

What am I doing wrong?
 
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  • #2
ParrotPete said:
VA=2*(cos(45)*ei-sin(45)*ej
VB = VB*(cos(45)*ei+sin(45)*ej)
I guess that's VB = vB*(cos(45)*ei+sin(45)*ej), to avoid the pun.
rA/B= 10*ei
ek, perhaps?
ω=ω*ez
What's ez? Do you mean ei?
Doing the calculations
VB cos(45) = cos(45)
You've lost me - where did that come from?
 

FAQ: Simple problem about relative motion.

1. What is relative motion?

Relative motion refers to the movement of an object in relation to another object or reference point. It describes how an object's position, velocity, and acceleration change in relation to a different frame of reference.

2. How is relative motion different from absolute motion?

Absolute motion refers to the movement of an object in relation to a fixed reference point, such as the surface of the Earth. Relative motion takes into account the movement of both the object and the reference point, and describes their changing positions in relation to each other.

3. What factors affect relative motion?

The main factors that affect relative motion include the velocities and directions of the two objects, the distance between them, and any external forces acting on the objects.

4. How do you calculate relative motion?

To calculate relative motion, you need to determine the velocities of the two objects and their distance apart. Then, use the formula v1 - v2 = vrel to find the relative velocity between the two objects. The direction of the relative velocity will depend on the directions of the individual velocities.

5. Why is relative motion important?

Relative motion is important because it allows us to understand and describe the movement of objects in relation to each other. It is crucial in fields such as physics, engineering, and navigation, where precise measurements and predictions of motion are necessary.

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