International system of units
Answer:
In coin card experiment smooth card is used so that the card can slide easily from glass
Answer:
60 boxes
Explanation:
The work done by lifting a single box is equal to the force applied (the weight of the box) times the displacement of the box:

Power is related to the work done by the equation:

where W is the work done and t is the time. In this problem, we are told that the power used is P=60.0 W, while the time taken is t = 1 min = 60 s, so the total work done must be

Therefore, the number of boxes that she has to lift in order to use this power is the total work divided by the work done in lifting each box:

Calculating speed as function of distance y is fairly easy. Once water leaves pipe it is under free fall which means that it is accelerating with gravitational acceleration "a".
V=Vo + Vff where Vff is speed gained due to free fall.


Calculating radius of stream is a little bit more complicated. Because water is accelerating as it falls it has to lower its radius. The reason for this is that water flow must be the same as one at the exit of pipe. Water flow is expressed in liters/meter^3
Because of this we write condition:
V1/V2 = A2/A1 where A2 and A1 are sections of water stream.
let V1 and A1 be the speed and section of water stream at the end of pipe.
A2 = V1*A1/V2