I have 2 questions that I am approaching, one seems very simple but I am still at a loss. The other I have attempted multiple times to no avail. Here they are:(adsbygoogle = window.adsbygoogle || []).push({});

1. An arrow, starting from rest, leaves the bow with a speed of 28.9 m/s. If the average force exerted on the arrow by the bow was increased 4 times and the arrow was accelerated over the same distance, then with what speed would the arrow leave the bow?

I know that the Sum(F) = ma, but since we only have the Vo here I do not know where to start, I have tried multiplying my figures by 4, but that does not work either.

2. Airplane flight recorders must be able to survive catastrophic crashes. Therefore, they are typically encased in crash-resistant steel or titanium boxes that are subjected to rigorous testing. One of the tests is an impact shock test, in which the box must survive being thrown at high speeds against a barrier. A 50-kg box is thrown at a speed of 320 m/s and is brought to a halt in a collision that lasts for a time of 7.1 ms. What is the magnitude of the average net force that acts on the box during the collision?

My work: What I did here was use the equations of Kinematics, but I am not sure if that is correct.

What we know:

m = 50kg

Vo = 320 m/s

V = 0

t = 7.1 (milliseconds) ms

I used the equation:

V=Vo + a(.71) <------ I converted that to seconds

0 = 320 + a(.71) = a = 450 m/s^2

I used a in this equation

a = F/m, so F = ma, which was 50kg(450 m/s^2) = 22500 N

This was wrong.

Any help is appreciated, thanks.

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# Average Forces and Newtons Laws

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