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Find the speed of a Block going up an incline

  • Thread starter Lucy90
  • Start date
  • #1
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Homework Statement


What is the speed after 5 seconds?
Given
Box1 : 400 kg
Box2: 100 kg
Initial velocity: 20 m/s
μk: .30
Angle of Incline: 25
Time: 5 seconds

Homework Equations


Force of Friction: (mg)(cos θ)(μ)
Effective Gravity: (mg)(sinθ)
F=ma
Vf = Vi + at

The Attempt at a Solution


For Force of friction I got 1066.9055
For Effective Gravity I got 1658.3540
Then I added the weight from the 100 kg block

Then I did Fnet = -1066.91-1658.35 + 981 = 500a
a = -3.49

Vf = Vi + at
Vf = 20 + (-3.49)(5)
Vf = 2.55

I'm not sure if this is correct
 

Answers and Replies

  • #2
gneill
Mentor
20,736
2,732
Hi Lucy90,

Welcome to Physics Forums.

Your numerical result looks fine, but the units are missing. Always be sure to include the units on numbers that are results (including intermediate results). It helps with checking, and markers will usually deduct points (or simply mark the answer wrong) if they are left out. It's good to get into the habit of always including them.
 

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