A car starts from rest and travels 5.0 s with a uniform acceleration of 1.5 m/s2. The driver then applies the brakes, causing the car to slow down at a rate of 2.0 m/s2. If the brakes are applied for 3.0 seconds, how fast is the car going at the end of the braking period and how far has it gone from the start?

Respuesta :

Answer:

1.5 m/s

32.25 m

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

a = Acceleration

s = Displacement

Equation of motion

[tex]v=u+at\\\Rightarrow v=0+1.5\times 5\\\Rightarrow v=7.5\ m/s[/tex]

The velocity of the car at the end of the acceleration period is 7.5 m/s

This velocity will be considered as the initial velocity of the decelerating stage

[tex]v=u+at\\\Rightarrow v=7.5-2\times 3\\\Rightarrow v=1.5\ m/s[/tex]

The velocity of the car at the end of the deceleration period is 1.5 m/s

[tex]s=ut+\frac{1}{2}at^2\\\Rightarrow s=0\times t+\frac{1}{2}\times 1.5\times 5^2\\\Rightarrow s=18.75\ m[/tex]

Distance traveled in the acceleration period is 18.75 m

[tex]s=ut+\frac{1}{2}at^2\\\Rightarrow s=7.5\times 3+\frac{1}{2}\times -2\times 3^2\\\Rightarrow s=13.5\ m[/tex]

Distance traveled in the deceleration period is 13.5 m

Total distance traveled is 18.75+13.5 = 32.25 m

Answer:

1.5 m/s

Explanation:

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