newton's first law of motion

FORCE

  • Definition: A force is any push or pull that causes a change in the motion of an object.

  • Types of Forces: Push and pull are opposite forces.

    • PUSH: Applied in one direction to move an object away.

    • PULL: Applied to draw an object towards oneself.

TYPES OF FORCE

  • Contact Force: Exists when two or more surfaces or media touch and interact.

  • Non-Contact Force: Present in nature always and does not require human intervention to exist.

MOTION

  • Speed: The length of distance traveled in a certain amount of time.

  • Velocity: The rate of change of displacement in a specified direction.

  • Acceleration: The rate of change of velocity caused by an unbalanced force.

SPEED

  • Example: A car traveling at a speed of 100 mph.

VELOCITY

  • Example: A car traveling at a velocity of 100 mph to the East.

ACCELERATION

  • Example: A car slows down at a stop sign and then accelerates again.

NEWTON'S FIRST LAW OF MOTION: LAW OF INERTIA

  • Law of Inertia: An object will remain at rest or in uniform motion unless acted on by an unbalanced force.

  • Inertia: The resistance of an object to change in its state of motion. It is mass-dependent.

    • Massive objects exhibit greater inertia, and smaller objects exhibit lesser inertia.

  • Mass: The amount of matter in an object, measured in kilograms (kg).

  • Weight: The amount of gravitational force acting on an object, measured in newtons (N).

  • Forces acting on an object at rest include normal force and gravitational force.

SUMMARY OF THE FIRST LAW

  • An object at rest will remain at rest, and an object in motion will continue in motion unless influenced by an unbalanced force.

NEWTON'S SECOND LAW OF MOTION: LAW OF ACCELERATION

  • Definition: The acceleration of an object is directly proportional to the net force acting upon it and inversely proportional to its mass.

  • Greater mass requires a greater force to achieve acceleration.

FORMULAS

  • Newton's Second Law: F = ma

  • Rearranged formulas:

    • a = F/m

    • m = F/a

  • 1 Newton (N) is equivalent to 1 kg·m/s².

  • Weight calculation: W = mg where g = 9.8 m/s².

SAMPLE PROBLEMS

  1. To find the net force required for a rocket to achieve an acceleration of 70 m/s² with a mass of 45,000 kg.

  2. To calculate the acceleration of a 0.60 kg ball hit with a force of 12 N.

  3. To determine the mass of an encyclopedia when a net force of 15 N causes an acceleration of 5 m/s².

  4. To solve for the mass of an object accelerating at 2.25 m/s² with a force of 7.80 N applied.

  5. To find the amount of force needed for an object of mass 1500 g to accelerate at 10.0 m/s².

  6. To calculate the acceleration of a 6.3 kg object with a force of 7.1 N applied to it.

NEWTON'S THIRD LAW OF MOTION: LAW OF INTERACTION

  • Principle: Whenever two objects (A and B) interact, they exert forces on each other.

  • Reaction Example: In every action, there is an equal and opposite reaction.

  • Interaction Examples: The flying motion of birds and the bouncing of a ball.