5-2 Resultant force (5.2)

Lesson goals:

Understand what a driving force is and

what a resisting force is.

Make calculations with a resultant force.

1 / 18

Slide 1: Diapositive

NatuurkundeMiddelbare schoolhavoLeerjaar 3

Cette leçon contient 18 diapositives, avec quiz interactif, diapositives de texte et 3 vidéos.

La durée de la leçon est: 45 min

Éléments de cette leçon

Lesson goals:

Understand what a driving force is and

what a resisting force is.

Make calculations with a resultant force.

Slide 1 - Diapositive

Resultant force (5.2)

Slide 2 - Diapositive

Driving force and resisting force

The two most important resisting forces:

- Air friction

- Rolling friction

and driving forces are

- gravity

- force of a motor

- pushing force

Slide 3 - Diapositive

Air friction

Air friction is due to the collision with

air particles

You can decrease air friction by:

- improving your streamline

- making your frontal cross-section

smaller

Slide 4 - Diapositive

Forces on a car...

= pushing foce

= frictional force

The pushin force and frictional force act in the opposite directions. is greater than

therefore

is to the right.

F^{​ p ​ ​}

F^{​ r ​ ​}

F p

F^{​ r ​ ​}

F^{​ r e s ​ ​}

Slide 5 - Diapositive

Resultant force causes acceleration

If the pushing force is equal to the frictional force then the resultant force is equal to 0 N

Then there is no acceleration THEREFORE

the car stand still OR
the car has a constant velocity

F^{​ p ​ ​} = F^{​ r ​ ​}

F^{​ r e s ​ ​} = 0 N

Slide 6 - Diapositive

Resultant force changes velocity

If the pushing force is greater than the frictional force the resultant force is greater than 0 N

The acceleration will be in the

direction of the resultant force.

This is also known as Newtons

first law of motion

F^{​ p ​ ​}

F^{​ r ​ ​}

Slide 7 - Diapositive

Resultant force changes velocity

If there is no pushing force only the frictional force is left and the resultant force acts opposite

to the the direction of motion.

The car will decelerate

(or rather have a negative

acceleration)

Slide 8 - Diapositive

Example

Slide 9 - Diapositive

Slide 10 - Diapositive

Slide 11 - Diapositive

Slide 12 - Diapositive

The resultant force can do three things

Accelerate an object (if the resultant force is in the direction fo motion),
Decelerate an object (if the resultant force is in the opposite direction of motion)
Change direction of an object

(when a force comes from the side)

Slide 13 - Diapositive

Slide 14 - Vidéo

Slide 15 - Vidéo

Slide 16 - Vidéo

Now try the following question in your digital method.

17, 18 and 19

Slide 17 - Diapositive

How did the lesson go? Any questions?

Slide 18 - Question ouverte