The mechanical advantage is defined as the ratio between the force produced by a machine and the force applied in input:

For the crowbar of the problem, the force applied in input is 40 N, while the force produced in output is equal to the weight of the rock that is lifted, so 400 N. Therefore, the mechanical advantage is
Answer:
Strong electrical currents in close proximity to the magnet.
Other magnets in close proximity to the magnet.
Neo magnets will corrode in high humidity environments unless they have a protective coating.
Explanation: Heat radiation
Answer:
375J of wasted energy
Explanation:
Efficiency=work output/work input×100%
50=w.o/750×100
750×50=100w.o
w.o=750×50/100
w.o=75×5
w.o=375J
Wasted energy=750J-375J
=375J
Aliter
If the machine is 50% efficient then it is also 50% inefficient
50%×750J=375J
Given Information:
Mass = m = 3 kg
Speed = v = 6 m/s
Radius = r = 2 m
Required Information:
Magnitude of the acceleration = a = ?
Answer:
Magnitude of the acceleration = 18 m/s²
Explanation:
The acceleration of the block traveling along a circular path with some velocity is given by
a = v²/r
a = 6²/2
a = 36/2
a = 18 m/s²
Therefore, the magnitude of the acceleration of the block is most nearly equal to 18 m/s².
Bonus:
The corresponding force acting on the block can be found using
F = ma (a = v²/r)
F = mv²/r
Answer:
c.
Explanation:
Electromagnetic waves are waves that are generated when an electric field and a magnetic field vibrate together. They are usually created whenever an electric field collides with a magnetic field.
In more generic terms for an electric field, the energy per unit volume is given by:
Energy density = 
For magnetic field:
Energy density =
∴
For the electromagnetic wave (u):
Total energy density is:

Due to the fact that the energy related with both fields is equivalent:
Then:
E = cB