LUS University Physics (University Physics) Halliday, Fundamentals of Physics, 1

Question

LUS University Physics (University Physics) Halliday, Fundamentals of Physics, 10e udy & Practice Assignment Gradebook ORION Downloadable eTextbook en Assignment FULL SCREEN PRINTER VERSIONBACK NEXT OURCES Chapter 02, Problem 015 biem blem biem A particle's position is given by x 19.0-12.00t+ 3t2, in which x is in meters and t is in seconds. (a) What is its velocity at t - 1 s? (b) Is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) Is the speed increasing or decreasing just then? (Try answering the next two questions without further calculation.) (e) Is there ever an instant when the velocity is zero? If so, give the time t; if not, answer "O". (f) Is there a time after t-3 s when the particle is moving in the negative direction ofx? If so, give the time t; if not, answer "O. blem (a) Number Units (c) Number Units blem (e) Number Units (f) Number Units SHOW HENT by LINK TO TEXT LINK TO SAMPLE PROBLEM INK TO SAMPLE PROBLEM MATH HELP MATH LELP MATH HELP

Explanation / Answer

Given,

x = 19 - 12 t + 3 t^2

a)we need to find velocity at t = 1

We know that,

v = dx/dt = d(19 - 12 t + 3t^2)

v = -12 + 6 t

at t = 1 s

v = -12 + 6 = -6 m/s

Hence, v = -6 m/s

b)Its is moving in the negative direction.

c)speed = + 6 m/s

d)decreasing speed

e)for finding out the instant,

v = 0 = -12 + 6 t => t = 2 s

Hence, at t = 2 s

f)No.

Hence, Ans = 0

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