Newton's Laws

• What is inertia?

  Inertia is the tendency of an object to resist changes in its motion.
• How is mass related to inertia?


  Mass is a measure of a body's inertia — the greater the mass, the greater its resistance to changes in motion.
• What happens to an object if the forces acting on it are balanced?

  The object remains at rest or moves at constant velocity.
• What is an unbalanced (resultant) force?

  A force that is not completely cancelled out by other forces, causing a change in motion.
• How does resultant force affect acceleration?

  Acceleration is directly proportional to the resultant force and inversely proportional to the object's mass.
• What is the difference between mass and weight?

  Mass is the amount of matter in an object (kg); weight is the gravitational force acting on it (N).
• What is the formula for weight?

  Weight (W) = mass (m) × gravitational field strength (g)
• What is the approximate weight of a 1 kg object on Earth?

  10 N, since gravity ≈ 10 N/kg on Earth.
• What is the formula for gravitational potential energy (GPE)?

  GPE = m × g × h (mass × gravity × height)
• What forces act on an object falling through the air?

  Weight (downward) and air resistance (upward).
• What happens when an object reaches terminal speed?

  Air resistance equals weight, so the object stops accelerating and falls at a constant speed.
• What does Newton’s Third Law imply about forces between two interacting objects?

  They exert equal and opposite forces on each other.
• Skydiver QER

  1. Accelerates as they fall
  2. As speed increases, so does air resistance
  3. Reaches Terminal velocity where the air resistance force and weight are equal so the speed is constant
  4. Parachute opens, increasing air resistance and slowing down the skydiver
  5. The skydiver continuous to slow down until a new terminal velocity is reached which is safe to land
• Newton's first law

  An object will remain at rest or at a constant velocity unless it is acted upon by an external resultant force.
• Newton's second law

  F = ma