Biomechanics 2 – Newton’s Laws of Motion2.2 A BALL OF A TIME!

What is a force? A push, pull or twist that causes objects to

move, speed up, slow down, stop or change direction.

Force = Mass x Acceleration

Force

Newton’s 1st Law of Motion

An object at rest tends to remain at rest unless acted upon by some external force.

An object in motion will stay in motion in a straight line until acted on by an external force.

Which of the following has the greater Inertia and why?

30kgs

20kgs

Answer: 30kg weight because it has a greater mass

Newton's first law

http://www.youtube.com/watch?v=BlFGN2zlDYc

Newton’s 1st Law of Motion

1.Basically inertia is an objects resistance to movement. Having a great deal of inertia can be an advantage in

some sports – Can you think of three?

Of course having a lot of Inertia can have a disadvantage in some sporting situations. How?

If you have a lot of Inertia you require a lot of force or effort to get moving.

Newton’s 1st Law of Motion

The ball will keep travelling until gravity/air resistance pulls it down or player blocks the ball.

Newton’s 2nd Law of Motion

2. When a force acts upon a mass, the result is acceleration of that mass.

Consider the following three balls:

a) If each is hit with the same amount of force, which one accelerates the most? Why?

The table tennis ball – because it is lighter

b) If the tennis ball is hit with gradually increasing force, what happens to its acceleration?

The acceleration will increase with increasing force

Newton's second law

https://www.youtube.com/watch?v=-KxbIIw8hlc

Newton’s 2nd Law of Motion

So considering this 2nd law we can say… The greater the force, the greater the

acceleration The smaller the mass the greater the

acceleration when a constant force is applied. The mass will accelerate in the direction the

force is applied.

How could you apply Newton’s 2nd Law to a sporting situations

Newton’s 3rd Law of Motion

3. For every action, there is an equal and opposite reaction.

a) When we apply a force to something, this is known as action force

b) The object we apply a force to, applies a force back a reaction force.

On the following pictures, draw in and label the two forces in action

actionreaction

actionreaction

Newton's third law

Part 1: Newton’s Law of MotionLaw #3

We can see pairs of forces working when we run on sand. We run forward and sand is kicked up behind us in the opposite direction.

What other example of this can you think of?

When a ball is bounced, it bounces back in a direction opposite to that in which it was dropped

Newton’s 3rd Law of Motion

The incoming ball is the Action Force.

Your body acts as a reaction force.

Because your body has the greater Inertia, the ball is the reaction

reaction

action

Can you apply the 3rd law to passing in netball?

Analyse this shoulder pass.

Where would you put the necessary arrows?

Come draw on the board