Explanation:
F = ma is the formula of Newton's Second Law of Motion. Newton's Second Law of Motion is defined as Force is equal to the rate of change of momentum. For a constant mass, force equals mass times acceleration.
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Answer:
Explanation:
The stunt will likely sustain serious injury in case of concrete blocks because the average force acting on the person will be more because concrete blocks do not squeeze to provide more time for the force to act on the body instead it acts for a small amount of interval.

As impulse is constant so time requires to act force on the body is more as compared to concrete block and thus average force in mattress case is less.
Protons and neutrons are packed together in a very small region called nucleus. Protons are positively charged and we know that like charges repel. Then how is it that protons are not repelling each other and flying away from nucleus?
You may think that gravitational force is holding all the protons together but it is not so. Gravitational force is many times weaker than repulsive force.
It is actually strong force which holds proton together. At this short distance, strong force comes into play and is several times stronger than the repulsive force.
Speed is v = d/t
Or speed is distance over time
So...
40min / 60min = 0.6667 or 2/3 --> Finding what proportion 40 minutes is to an hour or 60 minutes as we need the units of hours to match up
45km/h = d/0.6667h
d = (45)(0.667)
d = 30.0015 or 30km