a ball tied to a string is twirled around in a circle as shown. copy the diagram and draw a vector showing the direction of the ball's velocity and the direction of the centripetal force on the ball at each of the three points

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

you can cut your hand off if your not