The positions of objects A and B are graphed at right. Answer the following ques

Question

The positions of objects A and B are graphed at right. Answer the following questions and explain. a) Is the acceleration of object A positive, negative, or zero at t = 2 s? b) At t = 2 s, is object B speeding up, slowing down, or moving with constant speed? c) Is the acceleration of object B positive, negative, or zero at t = 2 s? d) Do the two objects ever have the same position? If so, when? e) Which object has the greater speed at t = 11 s? f) Find the average velocity of object B for the 20-second interval shown. g) Estimate the instantaneous velocity of object A at t = 15 s.

Explanation / Answer

a) as the slope of A is constant at t =2 s, so acceleration is zero.

b) as the slope is decreasing so B is slowing down

c) as B is slowing down in negative direction so accelaration is positive.

d) yes, at t = 18 s

e) A has zero slope os zero speed and B has positive slope so positive speed. so B has gretaer speed.

f) displacement for B = 100-(-100) = 200

average velocity = displacement / time = 200/20 = + 20 m/s

g) form 14 s to 16 seconds, displacement = 100-130 = -30m

time = 2 s

instantaneous velocity = -30/2 = -15m/s

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