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Old 01-12-2009   #2
MAS1

 
Join Date: Dec 2008
Posts: 249
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Quote:
Originally Posted by meow77212 View Post
What is the acceleration produced on an object if it changes its velocity from 36 cm/min to 288 m/h in 10 min ?

And

A driver was driving a car weighing 500 kg towards his home, covering a distance of 100 km in one hour. He realizes that he is late for a party and accelerates the motion of the car. After 10 minutes he is covering a distance of 2 km in one minute. How much force did the engine apply on the car to achieve the acceleration?


I am a graduate student majoring in early childhood education and I am required to take a science course. I took an "easy" course so I thought! I tried for hours to figure these questions out and I can't. Thank you for all your help!
1. Acceleration is defined as the change in velocity over time, or

a = delta v / delta t where delta means "change in"

First you need to make your starting velocity and ending velocity have the same units. Therefore,

288 m/h = 288 m/h x (1 hr/60 min) x (100 cm/1 m) = 480 cm/min

Change in velocity = 480 cm/min - 36 cm/min = 444 cm/min
Change in time = 10 min

accel = (444 cm/min) / (10 min) = 44.4 cm/min^2 (or 44.4 cm/min/min)


2. First find the acceleration as in problem 1.

100 km/hr = 100 km/hr x (1 hr/60 min) = 1.666667 km/min

Change in velocity = 2 km/min - 1.6666 km/min = 0.33333 km/min
Change in time = 10 min

accel = (0.33333 km/min) / (10 min) = 0.0333333 km/min^2

Now remember force = mass x acceleration = f =ma

So f = (500 kg) x (0.0333333 km/min^2) = 16.66667 kg-km/min^2

Units of force are Newtons (N) which are kg x m/sec^2 so converting gives:

16.6666667 kg-km/min^2 x (1 min/60 sec) x (1 min/60 sec) x (1000 m/1 km)

= 4.63 N

Hope this helps.
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