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The car's speed decreased linearly as a function of time.
The speed was 60 kph at t=1s and 40 kph at t = 5 s.
Create a function that describes speed as a function of time. At what time did the car's speed equal 0?
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The function is
f(t) = V - at, (1)
where V is the initial speed at t= 0, "a" is the rate of the speed decreasing, t is the time (in seconds).
We don't know V at t= 0 (it is not given), but we can easily find "a".
"a" is the ratio of the change of the speed to the elapsed time
a = = = 5 kilometer per hour per second.
Now from equation (1) we will find V
V - 5*1 = 60 ,
V = 60 + 5 = 65.
Thus the function is f(t) = 65 - 5t kilometers per hour. ANSWER
To find the stop time, write this equation
V = 65 - 5t = 0.
From the equation, t = 65/5 = 13 seconds from the beginning. ANSWER
Solved, with all necessary explanations.