The equivalent resistance of n resistors in series is given by:

In our circuit, we have three resistors of

each, therefore the equivalent resistance of the circuit is
Answer:
The average speed of the elevator going down in the abandoned mine is 17.722mph.
Explanation:
If the elevator takes 90 seconds to descend a height of 713m, the average speed of the elevator is:

And if 1m/s is 2.23694mph, the average speed is:
.
Answer:
86605.08 N
Explanation:
The equation to calculate the force is:
Force = mass * acceleration
The force and the acceleration does not have the same direction in this case, so we need to decompose the force into its horizontal component, which is the force that will generate the horizontal acceleration:
Force_x = Force * cos(30)
Then, we have that:
Force_x = mass * acceleration
Force * cos(30) = 25000 * 3
Force * 0.866 = 75000
Force = 75000 / 0.866 = 86605.08 N
Speed is the same as the initial: 25m/s.
*if* you need vectors though:
final velocity = (25*cos(35), -25*sin(35) ) m/s