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An object travels North at #5 m/s# for #8 s# and then travels South at #8 m/s# for #4 s#. What are the object's average speed and velocity?

Answer 1

Olivia Askew

The average speed is #=6ms^-1#
The average velocity is #=0.67ms^-1#

The total distance travelled is #d=(5*8)+(8*4)=40+32=72m#

The total time is #t=8+4=12s#

The average speed is

#barv=d/t=72/12=6ms^-1#

The displacement is

#Deltax=(5*8)-(8*4)=40-32=8m#

The average velocity is

#=(Deltax)/t=8/12=0.67ms^-1#

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Answer 2

Sebastian Acosta

The object's average speed is ( \frac{Total \ distance}{Total \ time} = \frac{(5 \ m/s \times 8s) + (8 \ m/s \times 4s)}{8s + 4s} = \frac{40m + 32m}{12s} = \frac{72m}{12s} = 6 \ m/s ).

The object's average velocity is ( \frac{Total \ displacement}{Total \ time} = \frac{(+40m) + (-32m)}{12s} = \frac{+8m}{12s} = \frac{2}{3} \ m/s ) north.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.