4.1.2

Newton's Laws

Test yourself

Newton’s 1st Law

Newton's 1st Law says that the velocity of an object will only change if a resultant force is acting on the object. This applies to a stationary (still) or moving object.

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Stationary (still)

  • If an object is stationary (not moving) and there is no resultant force acting on it, it will stay stationary.
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Moving

  • If an object is moving and there is no resultant force acting on it, the object will continue moving in the same direction at the same speed.
    • This means that the object will continue moving at the same velocity.
    • This also means that the velocity of an object will only change if a resultant force is acting on the object.

Newton's 2nd Law

A force may cause a mass to accelerate. This acceleration can be a change in speed, a change in direction or a change in both speed and direction. This is Newton's 2nd Law.

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Resultant force

  • The resultant force is the sum of all of the forces acting on an object.
  • The change in an object’s motion is caused by the resultant force.
  • If the forces acting on an object are unbalanced (not equal) it means that a resultant force is acting on the object.
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Resultant force equation

  • A resultant force causes an acceleration.
  • The acceleration can be calculated with this equation.
  • Resultant force (F) = mass (m) x acceleration (a).
  • This is Newton's 2nd Law.
  • Remember that the resultant force is the vector sum of all forces. You need to take into account their directions.

Jump to other topics

1Physical Quantities & Units

2Measurement Techniques

3Kinematics

4Dynamics

5Gravitational Fields

6Deformation of Solids

7Thermal Physics

8Oscillations

9Communication

10Electric Fields

11Current Electricity

12Magnetic Fields

13Modern Physics

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