A particle's acceleration is described by the function a(t) = (12 t-30) m/s?, where t is in s. Its initial conditions are xo = 0 m and vo = 0 m/s at t = 0 s. a. At what time is the velocity is 3m/s? b. What is the particle's position at that time?

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Chapter3: Motion Along A Straight Line
Section: Chapter Questions
Problem 48P: A particle has a contant acceleration of 6.0m/s2 . (a) If its initial velocity is 2.0 m/s, at what...
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A particle's acceleration is described by the function a(t) = (12 t -30) m/s?, where t
is in s. Its initial conditions are xo = 0 m and vo = 0 m/s at t = 0 s. a. At what time is
the velocity is 3m/s? b. What is the particle's position at that time?
%3D
Transcribed Image Text:A particle's acceleration is described by the function a(t) = (12 t -30) m/s?, where t is in s. Its initial conditions are xo = 0 m and vo = 0 m/s at t = 0 s. a. At what time is the velocity is 3m/s? b. What is the particle's position at that time? %3D
Expert Solution
Step 1 finding the time at which velocity is 3m/s

The particle's acceleration is described by 

a(t)=(12t-30) m/s2          --------(1)

Given initial conditions are 

x0=0 m  and v0=0 m/s    at t=0s

Since we know that the acceleration is given by 

a=dvdt

dv=adt

Integrating both sides

dv=adt+C   where C is the constant of integration

v(t)=(12t-30)dt+C

v(t)=12t22-30t +C       Here we use atndt=atn+1n+1     and adt=at

v(t)=6t2-30t+C         --------(2)

From initial condition, we know at t=0, v0=0

Using initial condition in (2), we get

0=6×02-30×0+CC=0

Therefore, equation 2 becomes 

v(t)=6t2-30t   --------(3)

Let us find the find the time at which v=3m/s. Substitute v=3m/s in (3) and solve t

3=6t2-30t6t2-30t-3=0

This is a quadratic equation in t

t=-(-30)±(-30)2-4×6×(-3)2×6  =30±900+7212  =30±97212  =30±31.1812t=30+31.1812  or t=30-31.1812t=61.1812=5.1 s   or t=-1.1812=-0.1s for solving quadratic equation we useax2+bx+c=0, thenx=-b±b2-4ac2a 

Since the time cannot be negative, we neglect the negative value of t

t=5.1s

Therefor, the particle's velocity is 3m/s at 5.1s.

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