Answer: B
Explanation: This can be easily done by inputting 5280 * 2.2.
Given: Change of x is 35.4m, Velocity Final=7.10 m/s, Velocity Initial=0m/s
Find: Acceleration
Analysis:
Vf²=Vi²+2aΔx (Velocity final squared equals Velocity initial squared plus 2 times acceleration times change of x)
(7.10 m²/s)²=(0 m/s)²+2a(35.4 m)
50.41 m/s²=(70.8 m)a
a=0.712 m/s²
I can't eliminate answers. Some of them are just wrong. A is incorrect. There is no such thing as a 1 pole magnet.
I wouldn't use B. If it is just a bar it is not a magnet.
C is the traditional answer
D is a space filler. It is just there to occupy a letter.
Answer
Any force greater 490N
Explanation
The force required just to make an object slide over a rough horizontal surface is any force greater that the static friction which given by;

Given;

Hence;
F = 0.5 x 100 x 9.8
F = 490N.
We will only need the coefficient of kinetic friction if we were asked to find the force required to keep the object moving uniformly. Usually, the force needed to keep an object moving uniformly over a rough surface is lesser that which is needed to start its motion.
In this problem, we were only asked to find the minimum force required to make the object move which we have done.