Newton’s first law of motion

• What should you be able to describe by the end of the video?

  Newton's first law of motion
• What do Newton's Laws of Motion describe?

  The effects of forces on motion
• How many laws of motion are there according to Newton?

  Three laws of motion
• What happens if the resultant force on a stationary object is zero?

  The object will remain stationary
• What occurs if the resultant force on a moving object is zero?

  The object continues moving at the same velocity
• What is the definition of velocity in this context?

  Speed in a given direction
• What does a balanced force on a stationary object indicate?

  The resultant force is zero
• What happens to an object with no forces acting on it?

  It remains at constant velocity
• What is the resultant force when two equal forces act in opposite directions?

  The resultant force is zero
• What does a resultant force cause an object to do?

  Change its speed or direction
• What happens when a resultant force of 50 Newtons acts on a stationary object?

  The object accelerates to the right
• What does a resultant force acting to the left do to a moving object?

  It causes the object to decelerate
• How can a resultant force change an object's direction?

  By acting at an angle to its motion
• What is the constant speed of the car mentioned?

  $15 \text{ m/s}$
• What must be true if a car is moving at a constant speed?

  There must be equal resistive forces
• What are the resistive forces acting on the car?

  Friction with air and road
• What does a resultant force cause an object's speed to do?

  Change from its current speed
• What is the effect of a resultant force on an object moving with constant speed?

  It can cause the object to accelerate
• What are the key points of Newton's first law of motion?

  • An object at rest stays at rest if no force acts.
  • An object in motion stays in motion if no force acts.
  • Velocity changes only if a resultant force acts.
• What happens when a resultant force acts on a stationary object?

  • The object accelerates in the direction of the force.
  • The speed of the object changes.
• What happens when a resultant force acts on a moving object?

  • The object can decelerate or change direction.
  • The speed of the object changes.