When a spinning star shrinks in radius, it speeds up. which of the following statements explains this phenomenon? a.)circular motion is always uniform b.)angular momentum is always conserved c.)a centripetal force always points outward d.)centripetal acceleration cannot change ( need answer asap will give brainliest)

B.)Angular momentum is always conserved

Explanation:

Angular momentum is given by:

where

m is the mass of the object

v is its speed

r is the distance between the object and the centre of its circular trajectory

In absence of external torques, angular momentum is always conserved. That means that for the spinning star, if its radius r decreases (because it shrinks), in order for L (the angular momentum) to be conserved, the speed (v) must increases, therefore the spinning star speeds up.

So, the correct choice is

B.)Angular momentum is always conserved

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: