Topic 4.2: Speed

• Science
• Middelbare school
• havo
• Leerjaar 2

Topic 4.2 

Speed

The unit for power is:

1. N
2. F
3. kg
4. Nm

Different forces act on an object. When is there a balance of forces?

1. if the forces have the same line of action
2. when the forces are opposite
3. when the forces are all equal
4. if the sum of the forces is 0 N

The left wins because it pulls with greater force.
What is the sum of force?

1. 40 Newton
2. 50 Newton
3. 60 Newton
4. 100 Newton

Power is

1. physical quantity
2. unit

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.

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:

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)]

distance can be calculated with the following formula

1. s = v/t Distance = speed / time
2. s = t/v distance = time/ speed
3. s = v x t distance = speed * time
4. t = s x v time = distance * speed

time can be calculated with the following formula

1. t= v/s time = speed / distance
2. t = s/v time = distance /speed
3. t = s x v time = distance * speed
4. t = s + v time = distance + speed

4.2 : Speed

The speed can be given in 2 different units

m/s  (meters per second)

km/h (kilometers per hour)

Calculate the average speed of the green car

In the first 3 hours he rode a distance of 60 km

so : s = 60 km and t = 3 hours

Use the formula v = s/t

v= 60/3 = 20 km/h

v = 20/3,6 = 5,6 m/s

Convert 100 km/h to m/s?

1. 27,8 m/s
2. 360 m/s
3. 103,6 m/s
4. 96,4 m/s

convert 18 m/s to km/h

1. 14,4 km/h
2. 65 km/h
3. 5 km/h
4. 21,6 km/h

The mass of Mohamed is 45 kg. What is his gravitational force, Fg

1. 350 N
2. 45 N
3. 441 N
4. 882 N

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)

What does this graph tell you?

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

How far is the object after 16 seconds?

1. 500 km
2. 1000 km
3. 0 km
4. 300 km

What is the speed of the object at 11 seconds?

1. 0 m/s
2. you can't tell
3. 500 m/s
4. 500 km/h

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?

1. 2 cm
2. 5 cm
3. 10 cm
4. 12 cm

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.

Homework

Finish exercises of 4.1: forces

Make exercises of 4.2 :  Speed

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