We can use Newton II here (where F=m*a), that F is the net (or resultant) force on the object, m is the mass of the object and a is the acceleration the object experiences.
This means, in this case there would be no friction and absolutely no other force which gives a component in the plane of motion, only then can you assume that F=804N.
Now using F= m*a
804 = 51.7*a
Therefore a = 804/51.7 = 15.55 m/s²
Here we can use the work energy theorem

here we know that

as it come to rest finally



now work done by friction force will be given as


Work done by spring force is given as



so now plug in all data above


so above is the friction coefficient
Answer:
The solution is attached in the pictures below
Explanation:
It starts or speeds up.
Some substances need certain amount of energy in order to react with each other.
Answer:
Option C is the correct answer.
Explanation:
Absolute pressure is sum of gauge pressure and atmospheric pressure.
That is

We have

Substituting

Option C is the correct answer.