Average acceleration of Suzie stopping with roller blades

[rr92890]

Suzie (of mass 52kg) is roller blading down the sidewalk going 36 mph. She notices a group of workers down the walkway who have unexpectedly blocked her path, and she makes a quick stop in 1.9 seconds. What is Suzies average acceleration? Answer in m/s^2. What force was exerted to stop Suzie? Answer in N.



I had converted miles to meters and divided it by the time in order to get the average, but the answer was incorrect. and for the second question I had multiplied the average by the weight, but that was also incorrect.

 

[Doc Al]

I had converted miles to meters and divided it by the time in order to get the average, but the answer was incorrect.

That part sounds right. Show exactly what you did.

and for the second question I had multiplied the average by the weight, but that was also incorrect.

That's not quite correct.

 

[cryptoguy]

did you convert hours to seconds? Aavg = delta V / delta t; so what you did should work..

 

[rr92890]

I changed 36 miles per hour to .01 miles per second which converts to 16.09344 meters per second. I divided that by 1.9 which equals 8.470231579 as the average acceleration. Then for the second part 8.470231579*52 = 440.4520421 N as the force exerted. I'm pretty sure that is what I did.

 

[Doc Al]

Your answers are perfectly correct. (Except for the unrealistic number of significant figures carried. Round off your final answers.)

 

[rr92890]

thank you!