Question

Suppose you’re eating in a restaurant where the dishes are shared at the table and all placed uniformly on a rotating disk-like surface. Model this surface as a thin disk of radius 44.1 cm. You can’t stop thinking about physics even though you’re out with your friends, and decide to calculate the mass of the rotating surface and all the food. If the surface is initially at rest and you exert a tangential force of 1.1 N on it, you observe that the food rotates at a speed of 0.7 rev/s after applying the force consistenty for 1.4 seconds. Find the mass of the disk wtih the food, in kg.

Answer: 1.5879

Suppose you’re eating in yet another restaurant where the dishes are shared at the table and all placed uniformly on a rotating disk-like surface. Model this surface as a thin disk of radius 48.2 cm. Someone else has spun the surface, such that it is initially at an angular speed of 0.4 rev/s. The surface and food has a combined mass of 4.3 kg. The waiter, to show off, throws a new dish of dumplings (mass 0.7 kg) onto the surface at a speed of 0.6 m/s, such that the dish lands on and sticks to the very edge of the surface moving in the same direction as the rotating food. While this is happening, you quickly calculate the final angular speed of the food so that you can predict its location at any time before others have a chance to eat the dumplings. What is this speed, in rad/s?

Answer: 2.201

Could you please write down the full solution?

Answer 1