8. a 300g mass hangs at the end of a string. a second-string hang from the bottom of that mass and supports a 900g mass. (a) find the tension in each string when the masses are accelerating upward at 0.700m/s2 . (b) find the tension in each string when the masses are accelerating downward at 0.700m/s2 .

First we need to analyse each mass and all the forces that interact with each of them. To do that, we use a free-body diagram and from that it'll be easier to analyse all the forces and write the mathematical relation between them, each free-body diagram is attached.

Now, we need to find a expression for the second tension and solve the equation.

Now, we replace the second tension in the first equation:

Therefore, with an upward acceleration, the tensions are and .

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Therefore, with downwards acceleration, tensions would be and .

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.