Topic 4.2: Speed

Topic 4.2 
Speed
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Topic 4.2 
Speed

Slide 1 - Diapositive

The unit for power is:

A
N
B
F
C
kg
D
Nm

Slide 2 - Quiz

Different forces act on an object. When is there a balance of forces?
A
if the forces have the same line of action
B
when the forces are opposite
C
when the forces are all equal
D
if the sum of the forces is 0 N

Slide 3 - Quiz

The left wins because it pulls with greater force.
What is the sum of force?
A
40 Newton
B
50 Newton
C
60 Newton
D
100 Newton

Slide 4 - Quiz

Power is
A
physical quantity
B
unit

Slide 5 - Quiz

4.2 : Speed
Learning goals
- I can describe the concept of speed and understand which
measurements and units are necessary to calculate it.
- I can calculate the speed (or distance or time) of an object
using the speed formula.
- I can convert speed between the units of m/s and km/h.
- I can create and interpret s,t-diagrams relating to an object’s
motion.

Slide 6 - Diapositive

4.2 : Speed
The speed (or velocity) of an object tells us how far it moves in a certain amount of time. It is calculated with the following formula:


Slide 7 - Diapositive

4.2: Speed
v for velocity in [m/s or km/h]

s for distance in [m or km]

t for time in [s or h(our)]

Slide 8 - Diapositive

distance can be calculated with the following formula
A
s = v/t Distance = speed / time
B
s = t/v distance = time/ speed
C
s = v x t distance = speed * time
D
t = s x v time = distance * speed

Slide 9 - Quiz

time can be calculated with the following formula
A
t= v/s time = speed / distance
B
t = s/v time = distance /speed
C
t = s x v time = distance * speed
D
t = s + v time = distance + speed

Slide 10 - Quiz

4.2 : Speed
The speed can be given in 2 different units
m/s  (meters per second)
km/h (kilometers per hour)


Slide 11 - Diapositive

Calculate the average speed of the green car

Slide 12 - Diapositive

In the first 3 hours he rode a distance of 60 km
so : s = 60 km and t = 3 hours

Slide 13 - Diapositive

Use the formula v = s/t
v= 60/3 = 20 km/h
v = 20/3,6 = 5,6 m/s

Slide 14 - Diapositive

Convert 100 km/h to m/s?
A
27,8 m/s
B
360 m/s
C
103,6 m/s
D
96,4 m/s

Slide 15 - Quiz

convert 18 m/s to km/h
A
14,4 km/h
B
65 km/h
C
5 km/h
D
21,6 km/h

Slide 16 - Quiz

The mass of Mohamed is 45 kg. What is his gravitational force, Fg
A
350 N
B
45 N
C
441 N
D
882 N

Slide 17 - Quiz

3.2 : Speed
An s,t -Diagram is a graph that shows the movement of an object.

it shows the distance (s) and the time (t)

Slide 18 - Diapositive

What does this graph tell you?

Slide 19 - Diapositive

In the first 25 seconds the object is moving 200 m
In the second 20 seconds the object has stopped
in the last seconds the object is coming back a 100 m

Slide 20 - Diapositive

How far is the object after 16 seconds?
A
500 km
B
1000 km
C
0 km
D
300 km

Slide 21 - Quiz

What is the speed of the object at 11 seconds?
A
0 m/s
B
you can't tell
C
500 m/s
D
500 km/h

Slide 22 - Quiz

I want to draw a force with a magnitude of 300 N.
The scale must be 1 cm = 60 N
How large should the arrow (vector) be?
A
2 cm
B
5 cm
C
10 cm
D
12 cm

Slide 23 - Quiz

4.2 : Speed
Learning goals
- I can describe the concept of speed and understand which
measurements and units are necessary to calculate it.
- I can calculate the speed (or distance or time) of an object
using the speed formula.
- I can convert speed between the units of m/s and km/h.
- I can create and interpret s,t-diagrams relating to an object’s
motion.

Slide 24 - Diapositive

Homework
Finish exercises of 4.1: forces
Make exercises of 4.2 :  Speed
12 to 21

Slide 25 - Diapositive