# 5-2 Resultant force (5.2)

Resultant force (5.2)
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Slide 1: Tekstslide
NatuurkundeMiddelbare schoolhavoLeerjaar 3

In deze les zitten 21 slides, met interactieve quiz, tekstslides en 4 videos. Lesduur is: 45 min

## Onderdelen in deze les

Resultant force (5.2)

#### Slide 2 -Video

Lesson goals:
• Understand gravitational acceleration.
• Understand what a driving force is and
what a resisting force is.
• Make calculations with a resultant force.

#### Slide 3 -Tekstslide

Gravitational acceleration
- In a lift moving with the same velocity as you
> it feels as if gravity is absent
- In a lift that is accelerating
> it feels as if there is a gravitational force

Therefore you can conclude that you can not seperate acceleration and gravitational force from each other.

#### Slide 5 -Tekstslide

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 6 -Tekstslide

Air friction
Air friction is due to the collision with
air particles
You can decrease air friction by:
smaller

#### Slide 7 -Tekstslide

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.

Fp
Fr
Fp
Fr
Fres

#### Slide 8 -Tekstslide

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
Fp=Fr
Fres=0N

#### Slide 9 -Tekstslide

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
Fp
Fr

#### Slide 10 -Tekstslide

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)

Example

#### Slide 15 -Tekstslide

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 19 -Video

Now try the following question in your digital method.

17, 18 and 19

#### Slide 20 -Tekstslide

How did the lesson go? Any questions?