Grade 5 | Science | Unit 4 - Concept 1 - Lesson 3 - What Is Gravity?

Описание: Welcome dear students!
What Is Gravity?
• You have learned that gravity is the force of attraction that exists between objects that have mass.
• We find the effect of gravity in everything around us.
• We know gravity is a force because we can see its effects around us, such as when something falls.
Examples:
• An egg could slip out of your hand and fall to the floor.
• When you drop a ball or a book, it falls down toward the ground.
• The force of gravity keeps us from floating into space like that happens with astronauts.
The effect of gravity on the planets:
• In space, there are big and small planets, where bigger planets have more gravity than that of smaller planets.
• The force of gravity keeps the planets revolve in their orbits or on fixed paths around the Sun.

Like the gravity of planets in space, we can say that:
On the Earth's surface, objects with large masses have more gravity than that of objects with small masses.
What goes up, must come down
Gravity changes the direction of anything you throw into the air.
Example:
• If you throw a ball into the air, the ball will go up into the air and then fall down back to the ground every time.
• As the ball flies through the air, its movement changes where, at first the ball is moving up, then its direction changes as it starts falling down toward the ground.
• The ball's direction changes because the gravity force is acting on the ball.
Note
Gravity does not only act on falling or moving objects but also, it acts on objects that do not move, such as a boy sits on a chair or a book on a shelf.
Gravity and mass
• All objects have gravity because they all have mass.
• Objects with greater mass exert greater force on objects around them as in the Earth-and-moon system, where:
• Earth is bigger than the moon and it has more mass so, Earth has stronger gravity than the moon.
• Also, the gravity of the moon causes the attraction of Earth toward the moon.
• The moon stays in a fixed orbit around Earth due to the gravitational force of Earth.
In this activity, we will investigate the angle at which an object is pulled toward the ground by the force of gravity.
Tools
• Several books
• Meterstick
• String
• Small weight
• Tape
• Protractor
Steps
1. Tie the string to the meterstick and use a piece of tape to hold it in place, then attach the weight to the end of the string.
2. Suspend the meterstick horizontally between the books, so that the string and the weight can move freely.
3. Measure the angle between the meterstick and the string using the protractor.
Observation
The angle will be 90° (because gravity always pulls objects downward).
4. Use several more books at the left side to tilt the meterstick up, then measure the angle between the meterstick and the string at the right side using the protractor.
Observation
When the meterstick is tilted upward, the angle between the meterstick and the string is less than 90° (acute angle).
5. Move some books away from the left side to tilt the meterstick down, then measure the angle between the meterstick and the string at the right side using the protractor.
Observation
When the meterstick is tilted downward, the angle between the meterstick and the string is more than 90° (obtuse angle).
Note
In this activity, the factors that cause the change of the angle measurements are:
1)The tilt of the meterstick up and down.
2)The movement of the string.
Conclusions
• All objects on or near Earth's surface are pulled down toward the center of Earth.
• As the tilt of the meterstick changed, the angle changed because the weight is always being pulled toward the ground.

#Gravity
#GravityForce
#Science_Grade5
#mrraoufashraf

Mr. Raouf Ashraf