Please Help Vector Forces in 2D

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  • #1
wr1015
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A shopper pushes a 7.3 kg shopping cart up a 13° incline, as shown in Figure 5-21. Find the horizontal force, F, needed to give the cart an acceleration of 1.63 m/s2.

ok, here is the formula to find horizontal force:

sum Fx= F1x +F2x = F1 + F2cos(theta), which also =mAx

if there are no forces given, how do i calculate F2cos(13degrees) and F2sin(13degrees)?
 

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  • #2
quantumdude
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wr1015 said:
if there are no forces given, how do i calculate F2cos(13degrees) and F2sin(13degrees)?

You would leave your answer in terms of the given symbols.
 
  • #3
wr1015
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Tom Mattson said:
You would leave your answer in terms of the given symbols.

my answer is supposed to be in Newtons, but my question is how to calculate acceleration in the x direction??
 
  • #4
quantumdude
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Duh, I didn't read the problem statement very carefully. :tongue: Yes, you will get an answer in Newtons.

Instead of resorting to a canned formula, you should draw a free body diagram and write down equations for the sum of the forces in the x and y directions. You've got the normal force, the applied force, and gravity.
 
  • #5
wr1015
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Tom Mattson said:
Duh, I didn't read the problem statement very carefully. :tongue: Yes, you will get an answer in Newtons.

Instead of resorting to a canned formula, you should draw a free body diagram and write down equations for the sum of the forces in the x and y directions. You've got the normal force, the applied force, and gravity.

ok so normal force = mass of cart x acceleration of gravity: F=(7.3kg)(9.81 m/s2) = 71.613N, what's the applied force?
 
  • #6
quantumdude
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wr1015 said:
ok so normal force = mass of cart x acceleration of gravity: F=(7.3kg)(9.81 m/s2) = 71.613N,

No, because the cart is on an incline.

whats the applied force?

That's the unknown.
 

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