Grade 4 | Science | Unit 2 - Concept 3 - Lesson 1 - Collision

Welcome dear students!
Example of collision :
A wrecking ball :
• It is a very heavy steel ball that swings on a cable.
• It is used to collide with walls of a building to help construction workers knock down walls or parts of buildings.
Collision in cricket :
• A cricket is a popular game all over the world.
• In cricket, a player uses a wooden bat to hit a ball.
• The cricket player holds a bat and moves it as the ball comes towards him at high speed to collide with the bat.
What happens to the energy of the moving bat when it hits the moving ball ?
• The bat transfers its kinetic energy to the ball.
• Then, the speed of the ball increases and the ball returns back in a different direction.
• This collision produces a popping sound and the player would feel the bat hitting the ball.
Safety equipment used during collision of cars :
1) Seatbelts :
They are used in cars to keep the driver and also the passengers from moving forward when the car stops suddenly, so seatbelts have saved thousands of lives.
2) Airbags :
Their structure :
Airbags are made up of thin nylon material folded into the steering wheel, seats, dashboard or doors.
Idea of operation :
During collision
• Airbags inflate automatically when sensors in the car detect a crash.
• A sensor tells the airbags to inflate and fill with a gas to provide a soft cushion.
After collision
• Airbags deflate almost as fast as they inflate, because they have holes (vents) to allow them to deflate, so the driver can get out of the car.
Their importance :
• Airbags slow the speed of the driver's motion forward.
• Airbags absorb the energy of the passengers on collision.
Give a reason for :
Airbags deflat quickly after few seconds of collision.
• Because they contain small holes (vents), through which the gas comes out, so the driver can get out of the car.
Collisions between trains and cars :
• There are many accidents in which a train hits a car that may be stuck on the train tracks.
• Trains are much larger than cars. Also, trains can travel at a high speed.
• It is more dangerous, as the force of the collision between the car and train increases.
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Mr. Raouf Ashraf