“Ph”ocus on Physics Force Problem Solving
Techniques
Steps highlighted in Bold MUST be done on problem
solving activities in order to receive full credit.
1. Determine if the object in question is “Changing its Motion (Net Force is 0, so
acceleration is 0)” or “Not Changing its Motion (Net Force is NOT 0, so acceleration is
NOT 0).” Do this TWICE. Once for Vertical plane and once again for Horizontal plane.
(For Inclined Planes you would do the Perpendicular and Parallel planes.)
2. Make a correct Free Body Diagram.
3. Make sure you did #2.
4. Write down Fg=mg for the Weight Vector on your FBD.
5. Assign directions to all forces and record them on the FBD.
6. Create a Force equation. Sum up all Forces on the FBD to determine Net Force.
ma
(NO NUMBERS-JUST FORCES-INCLUDE DIRECTIONS.) Write “ =
” on
the right side of your summation. Do this TWICE. Once for Vertical plane and once
again for Horizontal plane. (For Inclined Planes you would do the Perpendicular and
Parallel planes.)
7.
When plugging in numbers that need + or – in front of them, remember the
direction relationship between these 4 things: Net Force, Acceleration, Velocity and
Displacement.
Vector DIRECTION
Net
Force
Acceleration Acceleration
Velocity
Velocity
Displacement
Same – Speeding up
Opposite – Slowing
Same
down
Same
Perpendicular –
Moving in a circle
8.
This comes after the friction lab.
Ff = u FN
( Fun Equation)