# What is Rotational mecahnics: Definition and 11 Discussions

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2. ### Particle moving in a rotating disc

Well, I tried plugging the data in the formula. I know that ##\vec a_b = 0; \vec \omega=3 rad/s ; \vec r## can be calculated using trigonometry. Then I also know that ##v_{relx}= 10 cm/s##, ##a_{relx}=15 cm/s^2##, ##\vec {\dot{\omega}}=-10 rad/s^2##. But how do I get ##v_{rely}## and...
3. ### Torque of a rotating wheel on a static wheel

Homework Statement A uniform cylindrical wheel of mass ##m_{1}## and radius ##R_{1}## rotates with angular velocity ##\omega_{1}##. It lies a certain distance (along the same axis) from a static wheel of radius ##R_{2}## and mass ##m_{2}##. The wheels are then pushed against each other with a...
4. ### Moment of inertia in plane translation

I have a doubt in my mind regarding moment of inertia.in my textbook a question is somewhat like this The center of a disc of mass 'M' and radius 'R' is at a distance 'd' (here 'd' >'R') from a certain point 'O'.what is the moment of inertia of the disc about an axis perpendicular to the plane...
5. ### Just a confusion -- A mass falling onto a pivoting rod

Homework Statement A rod of mass ##M## and length ##l## is pivoted at the center(##O##) in horizontal position. An object of equal mass(having velocity ##v##) falls vertically on the rod at distance ##\frac{l}{4}## from ##O## and sticks to it. Find the angular velocity of the rod just after...
6. ### Pulley problem: Does the third pulley move up or down?

Homework Statement ) The pulley system in Figure 1.b consists of two pulleys of radii a and b rigidly fixed together, but free to rotate about a common horizontal axis. The weight W hangs from the axle of a freely suspended pulley P, which can rotate about its axle. If section A of a rough...
7. ### How Long Does It Take for 10 Meters of a Rolled Flag to Unwrap?

Homework Statement The flag is d=2mm thick and D=30 m long. We roll the flag and stick the short side of the flag (long side is 30m, short side's length is not given) on the ceiling so that the flag unwraps back to the ground. Flag is M=30kg. 1. Find the time it takes to 10 m of the flag to get...
8. ### What happens to a rod when an impulse is applied and it's floating in space?

1. a uniform rod of mass m and length l is placed horizontally on a smooth horizontal surface.An impulse is applied at one end perpendicular to the length of the rod. what is the velocity of centre of mass and angular velocity of rod just after the impulse is applied.
9. ### Struggling with Newton's Second Law Equations

Hello, I am a second year undergrad student majoring in Astronomy and Computer Science. I am having a hard time with my physics courses for the following reasons: 1) SmartPhysics is the text we use (if you can call it a text...). Basically it is an online HW and "pre-lecture" system that...
10. ### Conserving Angular Momentum (Rigid Body Dynamics)

Lets say i have a rod (length = L) hinged at one end (A).It is initially at rest.Now if an impulse (J) acts on the other end (B),can i conserve the angular momentum about A(the hinge)? that is can i write: JL=Iw?(I=moment of inertia,w=angular velocity) this is what i saw in the book. My Doubt...
11. ### Time of Fall for a Pencil Dropped at an Angle

Homework Statement Estimate the time it takes a pencil of length L=10 cm to hit the ground if initially the pencil makes an angle of 0.001 rad with the vertical. Take the gravitational acceleration to be 10m/s2 Details and assumptions Assume that the pencil is just a thin solid rod with...