Not sure how to do this one

  • Thread starter tonya
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  • #1
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Homework Statement



A box with a mass of 5 kg sits in the middle of the bed of a pickup truck moving with a speed of 90 km/h. The maximum force of friction between the box and the truck is 15N. If the truck were braked uniformly to a stop in 125 m, would the box move? Justify your answer mathematically.

Homework Equations



vf2= vo2 + 2ax???

The Attempt at a Solution



a= (vf2 - vo2) / 2x
a= (0-9) / 2(125)
a= -0.36
yes is would
am i even close?
 

Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
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Almost correct .

Calculate the acceleration of the truck - make sure you use consistent units.
Then draw a diagram of the forces acting horizontally on the box, remember f=ma
 
  • #3
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right so, 90 km/h is 25m/s. therefore acceleration [of truck] is equal to -0.1m/s2
 
  • #4
mgb_phys
Science Advisor
Homework Helper
7,774
13
Think you have a calculator error there
a = v2/ 2s = 252 / 2*125 ms-2
 

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