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# Question #2

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7. A helicopter’s speed increases from 25 m/s to 60 m/s in 5 seconds. What is the acceleration of this helicopter?
8. As she climbs a hill, a cyclist slows down from 25 mi/hr to 6 mi/hr in 10 seconds. What is her deceleration?

Jan 28, 2019

#1
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Acceleration is defined as (  change in velocity / change in time )

Velocity change =   Vf - Vo   = final velocity - original velocity  =  60 - 25 m/s =  35 m/s

Change in time = 5 s

35 m/s / 5 s = 7 m/s^2

2:   Same thing here        (6 m/hr - 25 m/hr)/ 10s   =  -19 m/hr / 10 s

Note that m/hr is not in the same units as  ' s '   so we will need to change either the m/hr or the time units so that they match

- 19 m/hr =   -19 m/hr  x  5280 f/m   x  1 hr/3600 sec =19*5280/3600 = - 27.8667 ft/sec

-  27.8667 ft/sec / 10 s   =  - 2.78667 ft/s^2    (negative acceleration because the cyclist is slowing down)

A NEGATIVE ACCELERATION is a POSITIVE DECCELERATION

Decceleration = 2.78667 ft/s^2

Jan 28, 2019
edited by ElectricPavlov  Jan 28, 2019
#2
+1

I managed to solve it on my own but thanks anyways

Jan 28, 2019