What is the mass of this object?

  • Thread starter chengbin
  • Start date
  • #1
26
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Homework Statement



A net force of 200N is applied to an object, causing its velocity to change from 30km/h to 20km/h in 2.3s.


Homework Equations



What is the object's acceleration? What is its mass?

The Attempt at a Solution



I got the correct answer for acceleration (-1.2m/s^2), but I'm having trouble with finding the mass.

I'm getting 199kg (m = 200N/1.2m/s^2), but the answer key says 170g. How is that correct?
 

Answers and Replies

  • #2
114
0
200/1.2 does not equal 199.

The answer should indeed be about 170kg.
Check your calculations again.
 
  • #3
26
0
Thanks.

Apparently I can't use my calculator properly.

I guess 170g is probably a typo in the book.
 
  • #4
114
0
they probably meant 170kg.
I got 167.8kg, which approximated to two significant figures gives indeed 170kg.
 

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