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POWER-UP 1/30

POWER-UP 1/30. What is the acceleration of an object that has a mass of 15kg and hits the ground with a force of 147N down. What is the name of the force that caused that acceleration?. FORCE NOTES. Definition of FORCE. A push or pull in a particular direction. How to notice a force.

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POWER-UP 1/30

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  1. POWER-UP 1/30 • What is the acceleration of an object that has a mass of 15kg and hits the ground with a force of 147N down. • What is the name of the force that caused that acceleration?

  2. FORCE NOTES

  3. Definition of FORCE • A push or pull in a particular direction

  4. How to notice a force • Forces cannot be seen • Their effects can be • Force causes acceleration • So, any time an object’s motion changes a force is acting on it.

  5. Forces act in pairs • For every force there is an equal and opposite force. (3rd law of motion) • So you can never have just a single force, there is always a second equal opposite force. • Often we only ask about / work with one of the forces, but there is always another force acting backwards on the other object.

  6. Force Units (N) • Force as the unit of Newtons • Abbreviated (N) • F = m*a so 1N = 1 (kg*m)/s2

  7. Multiple forces • The “Net Force” is the combination of all the forces acting on an object. • The Net Force is determined by combining all the forces together • When there are multiple forces on a single object use the Net Force to determine acceleration.

  8. Un/Balanced forces • When the Net force is ZERO N then the forces are called balanced and there is no acceleration • When the Net force is anything other than 0N then the forces are unbalanced and there is an acceleration

  9. Calculating the Net Force • Forces that go in the same direction you add (+) together • Forces that go in OPPOSITE direction you subtract (-) from each other and the larger one determines the direction of the Net Force

  10. PRACTICE 1 • A 150kg object has 1 person pushing on it with 180N of force north and another person pushing on it with 195N of force north. • What is the Net Force? • Are the forces balanced? • What is the object’s acceleration?

  11. PRACTICE 2 • A 20kg object has 1 person pushing on it with 80N of force east and another person pushing on it with 140N of force west. • What is the Net Force? • Are the forces balanced? • What is the object’s acceleration?

  12. Practice 3 • A 20kg object has 1 person pushing on it with 237N of force forward and another person pushing on it with 237N of force backward. • What is the Net Force • Are the forces balanced? • What is the object’s Acceleration?

  13. PRACTICE 4 • An 80kg object has 1 person pushing on it with 75N of force east and another person pushing on it with 135N of force west and a third person pulling it east with 100N of force. • What is the Net Force? • Are the forces balanced? • What is the object’s acceleration?

  14. Perpendicular Forces • Forces that are perpendicular (like north compared to west) DO NOT interact with each other. • Just like vertical and horizontal velocities are separate and do not interact; also perpendicular forces do not interact with each other.

  15. Perpendicular Practice 1 • A 30kg object has a force of 12N pushing west, a second force of 12N pushing east, a third force of 60N pushing north. • What are the two net force? • East west net force • North south net force

  16. Perpendicular Practice 2 • A 10kg object has a force of 3N pushing west, a second force of 5N pushing north, a third force of 15N pushing north, and a last force of 15N pushing east. • What are the two net force? • East west net force • North south net force

  17. Perpendicular Practice 3 • A man is pushing a 45kg object up the stairs. He is pushing with 500N up and 90N forward; however, gravity is pulling down with 441N. • What are the two net forces?

  18. Force Diagrams • Arrows represent forces. • A force arrow starts on the edge of the object and move away from the object in the direction of the force (regardless of being a push or pull) • Motion is not shown in a Force diagram, the net force implies the motion • When working with 2 or more objects, approach them each a separate objects and you will get the right diagram.

  19. Diagram Practice 1 • A 50kg object has 1 person pushing on it with 120N of force east and another person pushing on it with 240N of force west. • Diagram it • Determine net force • Determine acceleration

  20. Diagram Practice 2 • A 45kg object has a force of 20N pushing east, a second force of 20N pulling east, a third force of 60N pushing north. • Diagram it: • Determine net forces: • East/west net force • North/south net force • Determine both accelerations:

  21. Diagram Practice 3 • Object A is a 50kg object to the west of “Object B,” a 30kg object. Object A is pushing object B to the east with a force of 180N. Gravity is pulling object A down with a force of 490N and the floor is pushing Object A up with a force of 490N. Gravity is pulling object B down with a force of 294N and the floor is pushing Object B up with a force of 294N.

  22. How to determine Diagonals(for the adv physics class) • You will use • To determine the angletan-1(opposite / adjacent) = angle • To determine the magnitude of the diagonalopposite2 + adjacent2 = diagonal2 diagonal opposite angle adjacent

  23. How to refer to angles • Just having a 30 degree angle is not descriptive enough. • You must refer to the base line of the angle (east, west, north, south, left, right, up, down) • And you must also say which way the angle goes from the baseline • Example: 30 degrees north of east60 degrees down from left • The second direction represents the baseline (or adjacent) and the first direction represents the movement away from the baseline (or opposite)

  24. Diagonal Practice 1 • A 50kg object has a force pushing 200N to the north and a second force pushing 300N to the west. • Find the angle and magnitude of the net force

  25. Diagonal Practice 2 • A 30kg object has a force of 12N pushing west, a second force of 12N pushing east, a third force of 60N pushing north. • Determine the angle and magnitude of the net force

  26. Diagonal Practice 3 • A man is pushing a 45kg object up the stairs. He is pushing with 500N up and 90N forward; however, gravity is pulling down with 441N. • Determine the angle and magnitude of the net force

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