Easy physics problem?

  • Thread starter jabbie3
  • Start date
  • #1
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"Easy" physics problem?

Homework Statement



A truck of mass 9120 kg is traveling along a level road at an initial speed of 28.8 m/s and then slows to a final speed of 13.8 m/s. Find the total work done on the truck.

Homework Equations



W=1/2*mv2

The Attempt at a Solution



W=1/2*(9120)*(13.8-28.2)2

this was wrong...
 

Answers and Replies

  • #2
Delphi51
Homework Helper
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I agree that kinetic energy is the right approach.
Find the KE initially. Find the KE after it slows down. Take the difference. Note that the truck loses energy, so it must be doing work on the road or negative work is done on it.
 
  • #3
Nabeshin
Science Advisor
2,207
16


Work is not the kinetic energy, but rather the change in kinetic energy.
 
  • #4
cjl
Science Advisor
1,892
461


Rather than trying to combine the initial and final velocities into a difference of velocities, calculate the initial kinetic energy in its entirety, and do the same for the final kinetic energy. Once you have those, find the difference.
 

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