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Unit One: Force and Motion Lesson 1
Transcript of Unit One: Force and Motion Lesson 1
Lesson 1 – Motion in one direction
In 1964, Japan operated the first fast electric train. The speed of this train reaches 200 kilometers / hour.
This train was developed afterward so that its speed reached 270 kilometers / hour, and it was named " The Bullet Train ".
The difference between this " bullet train " and other trains is that each of its carts is operated by an engine of its own.
In this way, the train can move at extreme speeds more than the train that consists of a chain of carts pulled by one engine
In our daily
life, we describe the movement of some objects around us as fast and some others as slow. To compare the movement of objects, we should refer to the physical quantity that refer to this description. This quantity is called “speed”.
:-it is the change of object's location as time passes according to the location of another object.
is a physical quantity which is used to describe and measure the motion of object.
The two factors necessary for the description of motion
1- The distance that covered by the motion
2- The time taken by the moving body to cover this distance
: it is the distance moved through a unit time.
What the meant by
1-A train covers a distance 240 km in two hours
This means that the train moves with speed equals 120 km/h
2- A car moves with speed 150km/h
This means that the car covers a distance 150 km in one hour
3- The speed of a car equals zero
This means that the car is at rest
Kinds of speed
1- Regular (uniform) speed
If the speedometer’s indicator points to 70, this means that the car’s speed is 70 kilometer/hour which is approximately 20 meters/second.
If this reading stays constant during travel,
we say that the car moves at regular (uniform) speed.
This means that the car covers equal distances at equal periods of time.
What the meant by
1-An object moves at regular speed 400 km/h
This means that the object covers 400 kilometer each 1 hour
2- Irregular (non-uniform) speed
Or the change of object's position by unequal distances at equal periods of time.
Or the change of object's position by equal distances at unequal periods of time
It the total distance covered by moving object divided by the total time taken to cover this distance
1- A runner record a distance of 100 meters of a straight track in 10 seconds then he returned back waking he took 80seconds to come back to the starting point of running Calculate the runner's average speed while running and returning ?
What the meant by
1-the average speed of a moving car is 40km/h
This means that the total distance covered by the car divided by the total time taken to cover this distance equals 40
It is the speed of moving object relative to an observer
If there is a person in a car that moves at 80 kilometers in a certain direction.
Then, a car moves at 90 kilometers passed him in the same direction.
This means that if there is a person standing on the side of the road and he observes the speed of the moving cars
(this person is called the observer).
So : Observer may be ...
1- observer is at rest
2- observer moving in the same direction to the object
3- observer moving in the opposite direction to the object