# Out of curiosity

I have a question just out of curiosity, say that a car is driving along and as it travels, I start to measure the distance from when the car has traveled 8 seconds to 12 seconds, and find out that it is 64 meters. I do not know the distance it traveled before I started to measure(ie. before the 64 meters). What is my acceleration?

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#### brewnog

Gold Member
It's impossible to say.

You could have been travelling with constant velocity (acceleration=0), and covered 64 metres in those 4 seconds (at 16m/s) or you could have been accelerating with uniform acceleration of 8m/s^2 from 0m/s to 32m/s, or in fact anything in between.

#### HallsofIvy

Homework Helper
The time to cover a specific distance will tell you your average speed but you would need another interval, to get a different speed, to find an average acceleration.

#### daveyp225

In any of the basic kinematics equations you need at least three variables to solve for the rest of them. For example, you give only the displacement and the change in time. When I took Gen Physics, what helped me was to list everything the equation gives you, and if you have at least three of them you are good to go.

displacement (x_f - x_i)
start velocity (v_i)
end velocity (v_f)
change in time (t)
acceleration (a)

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