Quick and Easy Physics Question. Thanks!
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Quick and Easy Physics Question. Thanks!

[From: ] [author: ] [Date: 11-09-19] [Hit: ]
75s = 4.we know vf=2.55m/s,v0 = 2*avg vel -vf = 2*4.57-2.55=6.......
Just a homework problem I can't get...If you could show how you get the answers that would be useful in helping me actually understand it. Thanks a ton!!! All help is appreciated

A truck covers 40.0 m in 8.75 s while smoothly slowing down to final speed 2.55 m/s.

Find the A) Orginial Speed ?m/s and the B) Acceleration ?m/s2

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we know that dist = avg velocity / time

this tells us that avg velocity = dist/time = 40m/8.75s = 4.57m/s

we also know that avg vel = (vf+v0)/2

we know vf=2.55m/s, so that v0 is

v0 = 2*avg vel -vf = 2*4.57-2.55=6.59m/s

a=(vf-v0)/t = (2.55m/s - 6.59m/s)/8.75s =- 0.46m/s/s

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Original speed u = distance / time = 40.0m / 8.75s = 4.57 m/s (2d.p.)

Use v = u - at (v = final velocity, u = initial velocity, a = acceleration, t = time)

Acceleration a = (v - u)/t = (2.55m/s - 4.57m/s)/ 8.75s = -0.231 m/s^2 (negative denotes the deceleration)

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constant acceleration" a" ( 'slowing smoothly)


distance D = 1/2 a t^2 + Vot + Do

D given as 40 m. t given as 8.75 sec, assume Do = 40M and final D = O
or easier Do = 0 and D = 40m
be careful of the sign of a

solve by algebra or guess and calculate , guess again
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