Quick physics questions (1 Viewer)

[Twickel]

In 0.5mv^2 is v final velocity or average velocity.

Im doing an experiment I need to calulate the work, I got two force answers one is the force accelerating the car F=ma and the other is the force during the collision F=mv/t
Which one should I use to calculate the work?

 

[Aerath]

I believe that the velocity should be the final velocity, however, it's sorta hard to just measure the final velocity. Therefore, you should discuss it in the accuracy section of your Conclusion (or Analysis, whereever you happen to discuss accuracy).

I would use F = ma, and to calculate a, I would use v = u + at. But to be honest, it doesn't really matter which one you use, as long as you're consistent the whole way through the experiment. It also gives you something to discuss in your conclusion as to why F = ma did not equal F = m(v-u)/t.

 

[Twickel]

Modern vehicles have a crumple zone built in. During my experiment the crumple zone was modelled by adding an aluminium can to the front of the model car. In table #1 and #3 of my results the mass of the car with the can increased by 0.02kg, this in turn effects the momentum directly and impulse. For example if we refer to our trial with a ramp at 50° the force acting on the car was F=0.35x 3.51/0.06 F= 20.48N, Impulse is 20.48 x 0.06= 1.23 N.s and momentum is 0.35x3.51= 1.23 N.s. But when we add the aluminium can and carry out the experiment again on an angle of 50° the results change because of the mass of the can added. The results were as follows F= 0.37x3.51/0.15 F=8.66N, Impulse= 8.66 x 0.15= 1.30N.s , Momentum = 1.30N.s. Had the model crumple zone not changed the mass of the car like in modern day cars the Force acting on the car would have equalled 8.19N and Impulse and Momentum would have been equal to each other (1.23N.s) in both experiments (with and without crumple zone- aluminium can). Had the can not affected the mass of the car impulse and momentum would be equal hence in modern day vehicles crumple zones do not affect the strength of the impulse and momentum of a car during a collision. Ft=mv.
In modern vehicles because the crumple zone crumples during a collision the vehicles usually stops at the point of collision, before crumple zones were introduced when a car made impact with another object the car would rebound of that object and lose a little speed and would have a large momentum and impulse change e.g. Momentum and impulse would be equal but in the opposite direction. The crumple zone prevents passengers experiencing very strong opposite momentum and impulse changes by stopping the car from rebounding after a collision.

 

[Aerath]

Was there even a question in that block of writing? =\