A rock falls off a cliff and hits the ground after three seconds. The rock's velocity is 29.4 m/s when it hits the ground. What is its acceleration of the rock in the downward direction?

formula for acceleration= (final velocity - starting velocity)/ time elapsed

if the starting velocity was 0 m/s

if the final velocity is 29.4 m/s

time elapsed is 3 seconds

then a =(29.4-0)/3

=9.8 m/s^2

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.

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.