Answer:
B. 24.2 m/s
Explanation:
Given;
mass of the roller coaster, m = 450 kg
height of the roller coaster, h = 30 m
The maximum potential energy of the roller coaster due to its height is given by;



Therefore, the maximum speed of the roller coaster is 24.2 m/s.
Answer:

Decrease
Explanation:
I = Current = 3.7 A
e = Charge of electron = 
n = Conduction electron density in copper = 
= Drift velocity of electrons
r = Radius = 1.23 mm
Current is given by

The drift speed of the electrons is 

From the equation we can see the following

So, if the number of conduction electrons per atom is higher than that of copper the drift velocity will decrease.
Answer:
We show added energy to a system as +Q or -W
Explanation:
The first law of thermodynamics states that, in an isolated system, energy can neither be created nor be destroyed;
Energy is added to the internal energy of a system as either work energy or heat energy as follows;
ΔU = Q - W
Therefore, when energy is added as heat energy to a system, we show the energy as positive Q (+Q), when energy is added to the system in the form of work, we show the energy as minus W (-W).
A wave is a result of the disturbance in the equilibrium state. There are two types of wave, transverse and longitudinal. Transverse wave affects amplitude while longitudinal wave affects the frequency of the wave. As for the transverse wave, the magnitude of the perpendicular disturbance of the wave is directly proportional to the amplitude of the wave. The higher the transverse disturbance the higher the amplitude.