Answer:

Explanation:
The law of conservation of angular momentum states that angular momentum remains constant when there is no external moment or forces applied to the system. Let assume that star can be modelled as an sphere, then:

The final angular speed is:



Answer: I would choose options C and D
Explanation:
Ans: Let d is the distance from height to our eyes.
<span>Applying the Pythagoras theorem, we get,</span>
<span>Check image: </span>
Answer:
The mechanical advantage of the system is equal to 19.62
Explanation:
The ratio of the force produced by a machine to the force applied to it is called mechanical advantage. In other words it is the ratio of output force to the input force.
In this problem mass=200kg
applied force=100N
input force=100N
output force=
mechanical advantage 
It gives an idea about the efficiency of a mechanical device. It is indeed a measure of force amplification. In block and tackle system an assembly of ropes and pulleys is used to lift loads. When the moving block is supported by a greater number of rope sections the force amplification will be more.
Answer:
A. A resistor alters current and a switch turns current on and off
Explanation:
Resistor is the passive component that reduces the flow of current. Switch is the electrical device that turns on or off the current by closing and opening the electrical circuit.
Thus option A. A resistor alters current and a switch turns current on and off is correct.