Motion in one Dimension
Motion in one Dimension
Hello everyone,
Nice to meet you, welcome to my blog for physics.
Let's see above Figure 1.
Sorry for ugly picture.. I'm not good at drawing.
Assume that,
A driver is driving his car with 20 (m/s) velocity toward east.
The mass of car is 200 (kg) including the driver.
The car is on the straight road, and located 10 (Km) distance from his house.
Let's assume again that there is no fraction forces, no air resistance, no any kinds of resistances. We will learn about fraction force later, also resistance. For now I'll ignore them.
Look into the status of the car.
We are focusing on it. It has properties but not important regarding what kind of car, brand and color, etc,,. We are interested in it's physical properties. Exactly speaking, physical quantities.
On the Figure 1, I've mentioned 3 physical quantities. One is velocity and another is mass, the other is displacement.
There are two kinds of physical quantities, scalar and vector.
Scalar has only magnitude. But vector includes magnitude and direction. For instance, mass and temperature, luminous intensity, they have only magnitude. So they can be called scalars.The car on the Figure 1 has one scalar physical quantity, it's mass. Other 2 physical quantities, velocity and displacement are vectors. The magnitude of velocity is 20 (m/s). And its direction is east, or right direction.
About the displacement,
Before arguing displacement, we have to set origin of displacement. What do you think where is the origin on Figure 1? His house? His company? Actually the origin is it's up to you. If you want to set current car's position by origin for displacement, it's OK. you can set there by origin for the system.
Anyway the magnitude of displacement is the distance between the origin and the car.
Therefore the magnitude is 0 (m) from the current position of the car. And 10,000 (m) from the house, 5,000 (m) from his company.
Then let's discuss about the direction of displacement according to origins. When we see the Figure 1, we can catch that easily. From the house, the car is on west or left direction. From his company it's on east or right direction. Where do you want to set for origin? I'd like to set it on his house.
I'll give you a homework regarding physical quantities.
HW1) Write down 7 scalars and 7 vectors by hand writing.
I said the car is on the straight road. Not curved. Let's see below figure.
Figure 2
What is it? Yes. It's number line. We use it in mathematics frequently.
Number is increasing along to right direction.
Now, I will change the number distance by 5.
Figure 3
We can set that right direction is "+" (plus) direction and left direction is "-" (minus) direction.
I will put the Figure 1 on the number line like Figure 3.
Figure 4
Because I set the house by origin, the house is located in 0 number position. Anyway wherever we set position, the car and the company building are on the left side from the house relatively. So we can denote displacement vector like above.
The magnitude is 10 (km) and the direction is (-) (left or west)
For now let's consider physical unit. I think it's not difficult conception. So I will give you homework to study it.
First of all, there are physical quantities, and they have their own units. And there are base units made (abbreviated) by SI. SI means "International System of Units". Not IS! Why SI? Because it's from french, "Le Système international d'unités". So we are calling it by SI.
There are 7 SI base units. However on our Figures they are including only 3 base units.
m (meter), s (second), and kg (kilogram).
"m" is the standard of length.
"s" is the standard of time.
"kg" is the standard of mass.
HW2) Find out other 4 SI base units and what do they stand for?
SI set "kg" as the standard of mass. "kg" is 1,000 (g) in other words 103 g.
In this, the prefix "k" is a scale factor by 103 (1,000).
There are many SI prefixes representing scale factor.
HW3) Find out SI prefixes and explain them.
The car's velocity is (+) 20 (m/s), (+) stands for right direction. It means the car is moving 20 meters per one second toward (+) direction. So after 1 minutes (60 seconds), the car will move 1.2 km toward east from first position.
HW4) After one hour, how many distance will it move from first position.
The unit of velocity, ( m/s ) is a derived unit from SI base units. Most of physics units are derived units. So when we see physical unit, we can guess the meaning about physical quantity.
I'm telling you again now that this car is moving one straight line. We call it as one dimension motion.
Now I'll set a certain situation. Now is 5:30:00pm. Then when will the driver arrive his home?
The car must move 10 km more to arrive his home from current location.
Let's calculate how many time will it take.
10 (km) = 1,000 (m) = 20 (m/s) x t (s)
--> t (s) = 500 (s) = 8 (minutes) + 20 (seconds)
Therefore he will arrive at home at 5:38:20pm.
HW5) derive above result.
Hello everyone,
Nice to meet you, welcome to my blog for physics.
Figure 1
Let's see above Figure 1.
Sorry for ugly picture.. I'm not good at drawing.
Assume that,
A driver is driving his car with 20 (m/s) velocity toward east.
The mass of car is 200 (kg) including the driver.
The car is on the straight road, and located 10 (Km) distance from his house.
Let's assume again that there is no fraction forces, no air resistance, no any kinds of resistances. We will learn about fraction force later, also resistance. For now I'll ignore them.
Look into the status of the car.
We are focusing on it. It has properties but not important regarding what kind of car, brand and color, etc,,. We are interested in it's physical properties. Exactly speaking, physical quantities.
On the Figure 1, I've mentioned 3 physical quantities. One is velocity and another is mass, the other is displacement.
There are two kinds of physical quantities, scalar and vector.
Scalar has only magnitude. But vector includes magnitude and direction. For instance, mass and temperature, luminous intensity, they have only magnitude. So they can be called scalars.The car on the Figure 1 has one scalar physical quantity, it's mass. Other 2 physical quantities, velocity and displacement are vectors. The magnitude of velocity is 20 (m/s). And its direction is east, or right direction.
About the displacement,
Before arguing displacement, we have to set origin of displacement. What do you think where is the origin on Figure 1? His house? His company? Actually the origin is it's up to you. If you want to set current car's position by origin for displacement, it's OK. you can set there by origin for the system.
Anyway the magnitude of displacement is the distance between the origin and the car.
Therefore the magnitude is 0 (m) from the current position of the car. And 10,000 (m) from the house, 5,000 (m) from his company.
Then let's discuss about the direction of displacement according to origins. When we see the Figure 1, we can catch that easily. From the house, the car is on west or left direction. From his company it's on east or right direction. Where do you want to set for origin? I'd like to set it on his house.
I'll give you a homework regarding physical quantities.
HW1) Write down 7 scalars and 7 vectors by hand writing.
I said the car is on the straight road. Not curved. Let's see below figure.
Figure 2
What is it? Yes. It's number line. We use it in mathematics frequently.
Number is increasing along to right direction.
Now, I will change the number distance by 5.
Figure 3
We can set that right direction is "+" (plus) direction and left direction is "-" (minus) direction.
I will put the Figure 1 on the number line like Figure 3.
Figure 4
Because I set the house by origin, the house is located in 0 number position. Anyway wherever we set position, the car and the company building are on the left side from the house relatively. So we can denote displacement vector like above.
The magnitude is 10 (km) and the direction is (-) (left or west)
For now let's consider physical unit. I think it's not difficult conception. So I will give you homework to study it.
First of all, there are physical quantities, and they have their own units. And there are base units made (abbreviated) by SI. SI means "International System of Units". Not IS! Why SI? Because it's from french, "Le Système international d'unités". So we are calling it by SI.
There are 7 SI base units. However on our Figures they are including only 3 base units.
m (meter), s (second), and kg (kilogram).
"m" is the standard of length.
"s" is the standard of time.
"kg" is the standard of mass.
HW2) Find out other 4 SI base units and what do they stand for?
SI set "kg" as the standard of mass. "kg" is 1,000 (g) in other words 103 g.
In this, the prefix "k" is a scale factor by 103 (1,000).
There are many SI prefixes representing scale factor.
HW3) Find out SI prefixes and explain them.
The car's velocity is (+) 20 (m/s), (+) stands for right direction. It means the car is moving 20 meters per one second toward (+) direction. So after 1 minutes (60 seconds), the car will move 1.2 km toward east from first position.
HW4) After one hour, how many distance will it move from first position.
The unit of velocity, ( m/s ) is a derived unit from SI base units. Most of physics units are derived units. So when we see physical unit, we can guess the meaning about physical quantity.
I'm telling you again now that this car is moving one straight line. We call it as one dimension motion.
Now I'll set a certain situation. Now is 5:30:00pm. Then when will the driver arrive his home?
The car must move 10 km more to arrive his home from current location.
Let's calculate how many time will it take.
10 (km) = 1,000 (m) = 20 (m/s) x t (s)
--> t (s) = 500 (s) = 8 (minutes) + 20 (seconds)
Therefore he will arrive at home at 5:38:20pm.
HW5) derive above result.
