The answer is A. Reactivity
hope this helps
The frictional force is 39.4 N
Explanation:
We can solve this problem by applying Newton's 2nd law of motion: in fact, the net force acting on the block is equal to the product between its mass and its acceleration. So we can write

where
is the net force
m is the mass
a is the acceleration
Here we know that the box is moving with constant velocity, so its acceleration is zero:

This means that the net force is also zero:

The net force on the block is given by the applied force, forward, and the frictional force, backward:

where
is the applied force
is the frictional force
Therefore, solving for
,

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Answer:
(e)
Explanation:
At resonance we know that 
That is 



We have given resonance frequency f =4511 Hz and inductance L=1.82 mH
So 



So option e is the correct answer
Answer:
4.9N
Explanation:
The formula for weight is F = ma.
You plug in the mass of 0.5kg and an acceleration of 9.8 to get
F = (0.5)(9.8)
F = 4.9N
Answer:
friction reduces the efficiency of machines, thus we must reduce the friction force that is acting upon it.