1) The car overtakes the truck at a distance of 160 m far from the intersection.
2) The velocity of the car is 40 m/s
Explanation:
1)
The car is travelling with a constant acceleration starting from rest, so its position at time t (measured taking the intersection as the origin) is given by
![x_c(t) = \frac{1}{2}at^2](https://tex.z-dn.net/?f=x_c%28t%29%20%3D%20%5Cfrac%7B1%7D%7B2%7Dat%5E2)
where
is the acceleration
t is the time
On the other hand, the truck is travelling at a constant velocity, therefore its position at time t is given by
![x_t(t) = vt](https://tex.z-dn.net/?f=x_t%28t%29%20%3D%20vt)
where
v = 20 m/s is the velocity of the truck
t is the time
The car overtakes the truck when the two positions are the same, so when
![x_c(t) = x_t(t)\\\frac{1}{2}at^2 = vt\\t=\frac{2v}{a}=\frac{2(20)}{5}=8 s](https://tex.z-dn.net/?f=x_c%28t%29%20%3D%20x_t%28t%29%5C%5C%5Cfrac%7B1%7D%7B2%7Dat%5E2%20%3D%20vt%5C%5Ct%3D%5Cfrac%7B2v%7D%7Ba%7D%3D%5Cfrac%7B2%2820%29%7D%7B5%7D%3D8%20s)
So, after a time of 8 seconds. Therefore, the distance covered by the car during this time is
![x_c(8) = \frac{1}{2}(5)(8)^2=160 m](https://tex.z-dn.net/?f=x_c%288%29%20%3D%20%5Cfrac%7B1%7D%7B2%7D%285%29%288%29%5E2%3D160%20m)
So, the car overtakes the truck 160 m far from the intersection.
2)
The motion of the car is a uniformly accelerated motion, so the velocity of the car at time t is given by the suvat equation
![v=u+at](https://tex.z-dn.net/?f=v%3Du%2Bat)
where
v is the velocity at time t
u is the initial velocity
a is the acceleration
For the car in this problem, we have:
u = 0 (it starts from rest)
![a=5 m/s^2](https://tex.z-dn.net/?f=a%3D5%20m%2Fs%5E2)
And we know that the car overtakes the truck when
t = 8 s
Substituting into the equation,
![v=0+(5)(8)=40 m/s](https://tex.z-dn.net/?f=v%3D0%2B%285%29%288%29%3D40%20m%2Fs)
Learn more about accelerated motion:
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