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Net Force Particle Model

Net Force Particle Model. Newton’s Law Problems- unbalanced forces. Key Ideas . The amount by which the forces acting on an object are unbalanced is called the net force. When forces acting on an object are unbalanced, the object will accelerate.

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Net Force Particle Model

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  1. Net Force Particle Model Newton’s Law Problems- unbalanced forces

  2. Key Ideas • The amount by which the forces acting on an object are unbalanced is called the net force. • When forces acting on an object are unbalanced, the object will accelerate. • Acceleration is a change in velocity, and velocity includes both magnitude (speed) and direction, so a net force will change the speed and/or the direction of an object’s motion. • Forces may be balanced in one direction and unbalanced in the other.

  3. Newton’s 2nd Law • The net force on an object divided by its mass equals its acceleration • (Fnet) / m = a • Fnet = ma • Use Newton’s 2nd Law to qualitatively describe the relationship between: mass and acceleration, force and acceleration and mass and force. • If you double the mass, the acceleration will change by a factor of ….? • Use Newton’s 2nd Law to solve quantitative problems involving F, m and a. • Use a force diagram to find the net (unbalanced) amount of force. • List force and motion variables – knowns and unknowns. (next slide)

  4. Newton’s 2nd Law • List force and motion variables – knowns and unknowns. • Force Equation: Fnet = maForce Variables: acceleration, mass, net force • Motion Equations (Kinematic Eqns):Motion Variables: acceleration, initial velocity, final velocity, ∆t, ∆x (displacement) • Use what you know to solve for acceleration, then use it to solve for unknowns. Common variable: acceleration

  5. Sample Problems • Draw a force diagram for a block sliding to a stop. • Label the magnitude of the forces for a 5-kg block that is initially traveling at 30 m/s and slows to a stop in 5 sec.

  6. Sample Problems • Draw a force diagram for a 900-kg car that exerts 5000-N of traction force on a level road while being opposed by 1000-N of friction and drag forces combined. • Write the net force equation for the car. • Calculate the acceleration of the car.

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