High School Physics

Laws of Motion class 9 – statement, & concepts

Last updated on May 3rd, 2023 at 04:49 pm

Statement of three laws of Motion along with their concept building – that is the objective of this post.

Statement of three laws of Motion

Here we state the 3 laws of motion:

  • Newton’s 1st Law of Motion states that Every body continues in its state of rest, or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.
  • Newton’s 2nd Law of motion states that the rate of change of momentum of a body is proportional to the net force impressed, and this change is made in the direction of that force impressed.
  • Newton’s 3rd Law of Motion states that To every action, there is always an equal and opposite reaction.

Read more about the 2nd Law of motion

Read more about the 3rd Law of motion

Laws of Motion – some very important information

  • An object will not change its state of motion (i.e., accelerate) unless an unbalanced force acts on it. Equal and oppositely directed forces do not produce acceleration.
  • If no unbalanced force acts on an object the object remains at constant velocity or at rest.
  • Our mass does not change when we move to other planets, because mass is a measure of how much matter our body contains, and not how much gravitational force we feel.
  • Newton’s 3rd Law states for every force there is an equal but opposite reaction force. To distinguish a third law pair from merely oppositely directed pairs is difficult but very important.
  • Third law pairs must obey three rules: they must be of the same type of force, they are exerted on two different objects and they are equal in magnitude and oppositely directed.
  • Examples of third law pairs: A block sits on a table. The Earth’s gravity on the block and the force of the table on the block are equal and opposite. But these are not third-law pairs, because they are both on the same object and the forces are of different types. The proper third law pairs are: (1) earth’s gravity on block & block’s gravity on earth and (2) table pushes on block & block pushes on the table.
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