To me, that sounds like the "Law of Conservation of Energy".
Answer
D. move a small magnet back and forth within a section of the coiled wire.
Explanation:
i put that for the test and i got it right
Answer:
Reduce its weight
Explanation:
For an object on a flat surface, the maximum force of friction experienced by the object is given by:

where
is the coefficient of friction
W is the weight of the object
As we can see from the formula, there are two ways of reducing the friction:
- Decreasing
--> this coefficient depends on the material and on the roughness of the surface, so this can be changed by changing the properties of the surface
- Decreasing W, the weight --> this can be done by reducing the mass of the object
You said 2 revolutions every 0.08 seconds
1 revolution = 2pi radians.
A). The 'unit rate' is (2 rev) x (2pi / 0.08 sec) = 50pi radians/sec. =
157.1 radians per sec (rounded)
B). Radius of the wheel = 30 cm
Circumference = 2pi R = 60pi cm = 188.5 cm (rounded)
Rotation speed = 2 revs per 0.08 sec
Linear speed = 2 x 60pi cm per 0.08 sec
(120pi cm) / (0.08 sec) = 47.12 meters per sec
C). Frequency = (revs) per second
= (2) / (0.08 sec) = 25 per second .