4th second

vehicle A vehicle starts from rest and accelerates uniformly for 4 seconds to a speed of 8 m/s. Find the distance that the vehicle has traveled during the 4th second. a) 16m b) 9m c) 7m d) 4m

Solution. Posted on Saturday, January 17, 2015.

In order to solve this problem, we need to calculate the acceleration. Vf=Vi+a*t , where Vf – the final velocity, Vi – the initial velocity, a – the acceleration and t – the time. 8=0+a*4 So, a=2 m/s^2. The next step will be to calculate the position of the car after the first 3 s and the position of the car after the first 4 s. We will use the following equation: Xf=Xi+Vi*t+a*t^2/2, where Xf – the final position, Xi – the initial position and Vi – the initial velocity. Xf=0+0*3+2*3^2/2=9 m (after the first 3 s) Xf=0+0*4+2*4^2/2=16 m (after the first 4 s) Finally, we could calculate the distance that the vehicle has traveled during the 4th second. We have to subtract the position of the car after the first 3 s from the position of the car after the first 4 s. 16 m – 9 m = 7 m. The answer is c) 7m.

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