Performance data of a car owned by a student....

[Alexanddros81]

Homework Statement

Serway Physics Problem 2.43

Figure P2.43 represents part of the performance data f a car owned by a proud physics student. (a) Calculate the total distance traveled by computing the area under the red-brown graph line. (b) What distance does the car travel between the times t=10s and t=40s?
(c) Draw a graph of its acceleration versus time between t=0 and t=50s
(d) Write an equation for x as a function f time for each phase of the motion , represented by the segments 0a, ab, and bc.
(e) What is the average velocity of the car between t=0and t=50s?

Relevant Equations

See at solution

Hi. My question is for now why the equation of x as a function of time for phase of motion ab is $x=50t-375$?
Shouldn't that be $x=375+50t$?

 

[TSny]

Hi. My question is for now why the equation of x as a function of time for phase of motion ab is $x=50t-375$?
Shouldn't that be $x=375+50t$?

What are the values of $x$ and $t$ at point $a$? Do these values satisfy your equation?

 

[Alexanddros81]

At point a the value of x=375m and value of t=15s.
These values don't satisfy my equation.
But they satisfy the equation $x=50t-375$.

 

[TSny]

At point a the value of x=375m and value of t=15s.
These values don't satisfy my equation.
But they satisfy the equation $x=50t-375$.

Right. Can you see why your equation is not correct?

 

[Alexanddros81]

Right. Can you see why your equation is not correct?

No. Can you explain?

 

[TSny]

Keep in mind that the symbol $t$ denotes the time that has elapsed since the beginning of the motion, not the time that has elapsed since reaching point $a$. Your equation would be correct if written in the form

x = 375 + 50$\Delta t$

where $\Delta t$ is the time elapsed since reaching point $a$.