Is my teacher wrong? Problem dealing with forces.

  • Thread starter Thread starter Kinermatics
  • Start date Start date
  • Tags Tags
    Forces Teacher
Click For Summary
SUMMARY

The discussion centers on resolving forces in a physics problem, specifically analyzing net forces in the x and y directions. The correct equations are established as Fnetx = 20N - Fx (where Fx is 0) and Fnety = Fy - 50N (with Fy = +25N). The confusion arises from the signs associated with the forces, leading to a miscalculation of the net force. Ultimately, the correct net force is determined to be 77.5N, emphasizing the importance of accurately applying the signs of forces in calculations.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with vector addition and subtraction
  • Knowledge of force notation and directionality
  • Basic algebra skills for solving equations
NEXT STEPS
  • Review vector addition in physics problems
  • Study the concept of net force and its calculation
  • Learn about free-body diagrams and their applications
  • Explore common mistakes in force calculations and how to avoid them
USEFUL FOR

Students studying physics, educators teaching force dynamics, and anyone looking to improve their problem-solving skills in mechanics.

Kinermatics
Messages
13
Reaction score
0

Homework Statement


Problem is in the picture


Homework Equations


The teacher told us the
Fnetx = 20N - Fx (Fx is 0)
Fnety = Fy - 50N (Fy = +25N)


The Attempt at a Solution


My answer was 32N. But my teacher said the answer was C. which was 77.5N. He got it because Fnety = 75N for him. But that to me doesn't make sense since the Fy and 50N are pointing in opposite directions, won't Fnety be = -25N?
 

Attachments

  • forces.jpg
    forces.jpg
    25.5 KB · Views: 539
Physics news on Phys.org
Oh nvm i think i got it. I think he meant to put that:
25N = Fy - 50 huh? Darn and to think i could prove a teacher wrong ;"D
 
Welcome to PF.
Kinermatics said:
Oh nvm i think i got it. I think he meant to put that:
25N = Fy - 50 huh? Darn and to think i could prove a teacher wrong ;"D
Glad it worked out finally. The key here was to think carefully about which sign (+ or -) goes with each force -- including Fnety, which we know is + because the object accelerates in the +y direction.
The teacher told us the
Fnetx = 20N - Fx (Fx is 0)
Fnety = Fy - 50N (Fy = +25N)
It pays to be careful -- those forces in parentheses should read (Fnetx is 0) and (Fnety = +25N)
 

Similar threads

Calculating Net Force on a Wheel: Magnitude and Direction | 0.350 m Radius
  • · Replies 4 ·
Replies
4
Views
2K
Torque on a Pivot Point With Multiple Forces and Different Directions
  • · Replies 6 ·
Replies
6
Views
2K
What if check: Am I calculating tension wrong?
  • · Replies 3 ·
Replies
3
Views
2K
Which force acts perpendicular to the side faces of an axe head?
  • · Replies 6 ·
Replies
6
Views
2K
Measuring the coefficient of friction
  • · Replies 7 ·
Replies
7
Views
3K
Coulomb's Law Problem and net force
  • · Replies 3 ·
Replies
3
Views
3K
Why Did I Get the Pulley Tension Forces Wrong?
  • · Replies 12 ·
Replies
12
Views
3K
Please help with this suggested solution involving electrostatic press
  • · Replies 14 ·
Replies
14
Views
2K
Find the magnitudes of all of the forces acting on the sled
  • · Replies 5 ·
Replies
5
Views
2K
Why Are My Calculations for Force on a Charge Not Matching Up?
  • · Replies 5 ·
Replies
5
Views
3K