Resultant Forces

What effect does an overall (resultant) force have on an object?

What forces are being shown by these pictures?What is force measured in?

Call my Bluff

Resultant force – what happens as the result of a force.

Resultant force – the overall force on an object.

Resultant force – a force which results from something moving.

Learning Outcomes

• explain that when two objects explode apart they both experience a force .

• explain that forces always occur in pairs, one on each of the objects in an interaction.

• explain that, in an interaction pair of forces, the force on the first object will be equal in size and opposite in direction to the force on the second object

• show how the motion of rockets and jet engines is caused by an interaction pair

What effect does an overall (resultant) force have on an object?

If gravity pulls us down, why don’t we sink into the ground?

Explain that forces always occur in pairs, one on each of the objects in an interaction.

Is gravity acting on this apple?

Gravity is an “action at a distance” force.Q. Can you name another one?

Q. Why does the apple eventually fall?

explain that, in an interaction pair of forces, the force on the first object will be equal in size and opposite in direction to the force on the second object

Check point

• Which of these is not a “contact force”?

1) Friction 2) Weight 3) magnetism

Scrum it

• England smashed Australia in the Autumn internationals this year, partly thanks to their scrums, but why were they better?

• http://www.youtube.com/watch?v=J3YehLVpBE8

explain that forces always occur in pairs, one on each of the objects in an interaction.

NEWTON’S FIRST LAW

An object will remain at rest(or continue to move at a constant speed), unless it is acted on by an unbalanced force.

What implications does this law have? What effect does an overall (resultant) force have on an object?

Check point – which is the best definition of a resultant force?

Forces that equal zero.

When 1 force results in another.

The sum of forces acting on an object.

1 2 3

What effect does an overall (resultant) force have on an object?

Mini white boards at the ready

• Be prepared to draw force diagrams showing the pairs of forces !

• A stationary car.• A car where the driving force is bigger than the resistive forces.

• A helicopter taking off

• A train moving at a constant speed.What effect does an overall (resultant) force have on an object?

Complete the worksheet

Forces in Explosions

• http://www.youtube.com/watch?v=0Y14kEY-6fk

1) Draw an explosion. E.g. a firework

1) Why have you drawn it that way?

What forces are acting on this cannon

• Gun Recoil

Rockets

• http://www.youtube.com/watch?v=FzCsDVfPQqk

1) Watch the video and draw a diagram to show the forces acting in a rocket launch.

Rockets

• http://www.youtube.com/watch?v=FzCsDVfPQqk

1) Watch the video and draw a diagram to show the forces acting in a rocket launch.

Lets investigate

• http://www.youtube.com/watch?v=1jRK5vG3tkc

• Make a hover craft

• How does it work?

What effect does an overall (resultant) force have on an object?

Task – choose 1 or more of the following to complete – (choose something in your

learning style)

• Complete the worksheet on resultant forces

• Draw and fully label 5 examples of situations where forces are used e.g. a car accelerating, a car moving at a constant speed.

• Create a revision poster (for you) about resultant forces.

HIGHER ONLY Extension complete the misconceptions worksheet. (A/ A*)

What effect does an overall (resultant) force have on an object?

Plenary

Who is the strongest in this room?! … sorry Who is the most HENCH in this room.

What effect does an overall (resultant) force have on an object?

Can we walk on water?

• Watch the clip and see if you can make any suggestions.

• http://www.youtube.com/watch?v=Lm2pkeFJzVI

What effect does an overall (resultant) force have on an object?