How do I find the instantaneous velocity at times 0.55 s?

Question

anonymous · Answer

Time (s)                    0.0         0.20        0.30      0.40        0.50      0.60
Position (cm [W])       0             25           75         75           75          0

turingtest · Answer

You cannot get instantaneous velocity from this information, only average. The average velocity between t=0.5 and t=0.6 is (75-0)/0.1=750.

turingtest · Answer

sorry average velocity is  (0-75)/0.1=-750

turingtest · Answer

If you assume acceleration to be constant during this time you could infer that halfway through this interval (at t=0.55) the speed would be -350, but that info is not given.

anonymous · Answer

Yes you can.. I've done it using slope but I don't know if it's right.

anonymous · Answer

is it going to be .10 s = 10 s?

turingtest · Answer

Like I said, IF you assume the acceleration to be constant that gives you a constant slope between 0.5-0.6 seconds. since the velocity changes during this time from 75 to 0 the average acceleration is -750. Assuming a constant slope this gives the answer of v(5.5)=-350.

Note though that this is NOT instantaneous velocity, it is an approximation based on an assumption not given: that the acceleration is constant. If this is the way you are used to doing these kinds of problems you may be happy to call this the instantaneous velocity, but know that unless you are told either the motion function, or at least that the acceleration is constant, this method is useless for anything other than a "linear approximation" (the term given to approximating a function in [a,b] based on the assumption the slope is constant in that interval).