physics

find the average of a block being propelled propelled by an elastic band.
We know it is uniform acceleration.

my attempt on this problem
Measure the force applied of elastic band with a newton scale. The more you strecth the farther the distance the block will travel after you let it go. In my case my Fa was 6N. i proposed this idea to my teacher but he said the as the elastic band destreches after you let it go the force become 6,5,4,3,2. I am wondering if this is a correct way of finding the Fa. Then i would perfrom three trials to find the average.To find the average i would perform trials 2 times and divide them by three to find the average of d,t,forceapplied. i would find the distance,and time and assume V1 is 0. Can i assume V1 is 0 since it is in rest? my teacher looked puzzled i and i sure v1 is not 0. so then using v1,d,t, i would find v2 when it reaches the final velocity. then i would find the Acceleration acting on the block by using v1,v2,d,t. then i would find force normal by entering this fn=Mag
which would be mass x acceleration acting on block x acceleration due to gravity. i don't know how to go about finding force of friction because i can use this equation. FF=uFn.
One more question
can i find Fnet=Ma since i am going to find acceleration. will finding Fnet help me out?
thanks. Any suggestions ar welcome. Sir/Mam if u have any links on average force of friction please include them. i am been trying to tackle this problem forever.

What makes you think it is uniform acceleration. To get uniform acceleration, your force has to be constant, and as your teacher pointed out, force is not constant.

I have no idea what you are trying to do. Is it to measure the force of friction?
IF so, did I answer this? Ket me go back: Assume the rubberband is elastic (it is near so). THe potential energy stored in it is 1/2 k x^2 You can measure k pretty easily (force=kx, use a spring scale to measure the force at some x).

Now, set the potential energy of the rubber band (stretched x cm) equal to the work done on friction.

1/2 kx^2= Fricionforceaverage*(x+ distance) where distance is the amount the block traveled beyond the unstretched point, and x is the distance it traveled with the rubber band).
Solve for the average friction force.

This setup, done three times, will give reasonable results.

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