The answer is D using the work formula
W= F•d but if it was against gravity, it would be 0 if gravity is exerting the same amount, I would pick D using the formula, but I'm not so sure sorry
Answer:



Explanation:
g = Acceleration due to gravity = 
= Angle of slope = 
v = Velocity of child at the bottom of the slide
= Coefficient of kinetic friction
= Coefficient of static friction
h = Height of slope = 1.8 m
The energy balance of the system is given by

The speed of the child at the bottom of the slide is 
Length of the slide is given by


The force energy balance of the system is given by

The coefficient of kinetic friction is
.
For static friction

So, the minimum possible value for the coefficient of static friction is
.
Answer:
m = 35 g
Explanation:
The specific heat of a material can be calculated by the following formula:

where,
C = Specific Heat of Wax = 220 J/g
Q = Amount of Heat Supplied by the Heater = 7700 J
m = mass of wax melted = ?
Therefore,

<u>m = 35 g </u>
You could use a magnetic generator or you could use hydraulic power