Gravity and Friction as Forces

Gravity and Friction Affect Movements of Objects

Science 6 Quarter 3-Week 1

Science 6 Quarter 3-Week 1

Lesson 1

Kinds of Forces

Lesson 2

Gravitational Force

Lesson 3 Frictional Force 

Multiple Choice

Which of the following is needed to make an object start or stop moving?

• force

• friction

• gravity

• motion

Multiple Choice

A man tries to push a big box away but he cannot move it. Of the following forces,

which causes this to happen?

I. Electrostatic Force

III. Gravitational Force

II. Frictional Force

IV. Nuclear Force

• I and II only

• II and III only

• I and III only

• I, II and III only

Multiple Choice

Why is parachute important to a skydiver?

• It directs his motion.

• It makes him fall faster.

• It slows down his motion to have a safe landing.

• It keeps him appear beautiful as he falls down.

Multiple Choice

4. Why does a car travel faster in going down than in going up?

• It is being pushed by the wind.

• It is being pulled by the weight of the car.

• It is moving against gravity.

• It is moving towards gravity.

Multiple Choice

Raven was tired in climbing up the stairs. Why do you think it is difficult for her to

climb up the stairs rather than to go down the stairs?

• She is against gravity.

• She goes with gravity.

• She moves downward.

• She moves upward.

Multiple Choice

Why did a ball thrown to the air falls back to the ground?

• Acceleration caused the ball to move fast.

• Air caused the ball to fall on the ground.

• Gravity caused the ball to fall.

• D. The weight of the ball made it move faster.

Multiple Choice

If the distance between two bodies is doubled, the gravitational force between

them is _____.

• increased by 2

• increased by 4

• increased by 3

• increased by 5

Multiple Choice

Why does a ball cannot be roll continuously on a rough surface?

• The rough surface is not made for balls to roll.

• The force which enables the ball to move is released.

• The rough texture of the surface blocks the movement of the ball.

• The rough texture of the surface permits the movement of the ball.

Multiple Choice

Which shows that friction is undesirable?

• Approaching a stoplight.

  
  

• Lighting a matchstick.

• Pushing a furniture.

• Walking on wet floors

Multiple Choice

A bicycle moves faster on a cemented road than on a bumpy road. Why?

• Friction is greater on a cemented road.

• Friction is lesser on a cemented road.

• There is no friction on a cemented road.

• The bicycle can roll only on a cemented road

Have you ever played with marbles?

• Marbles can move if you give them a push.

• When a marble hits another marble, the other marble changes its position.

• A force is a push or pull, that starts, stops or changes the direction of an object. It is the action exerted by a body on another, which is manifested in its motion.

• 
  

Kinds of Forces

People who travel in the outer space experience many kinds of forces. These

forces also exist around us on Earth. These forces are gravitational, magnetic, electric,

and strong and weak nuclear force. The four forces are called universal forces. 

1. Gravitational Force

➢ It is a force that pulls objects towards one another.

➢ It is the universal force that affects the bigger and the smaller object.

The strength of gravitational force depends on the amount of mass in an object and the distance between objects. If the mass of both objects is very small, the gravitational force between them is extremely small. 

Gravitational force is also affected by distance. When objects are closer together, the gravitational force is greater, but as the distance increases, the gravitational force decreases.

2. Magnetic Force

➢ It is a force that causes objects to attract or repel each other.

➢ It is the force shown when magnets of iron are attracted to each other.

For magnets, unlike poles attract, like poles repel

3. Electric Force

➢ It is the force that exist between charged particles.

➢ Objects with different charges attract each other, and objects with the same charge repel each other.

➢ It is much stronger than gravitational force.

➢ It causes some objects to come together and others to stay apart. 

4. Nuclear Force

➢ It is the force that holds the particles in the nucleus together.

➢ Strong nuclear force is one type of nuclear force.

• Holds the nuclear particles together by holding the quarks together.

Quarks are smaller particles in neutrons and protons.

• It exists in very short distances. When this strong nuclear force breaks, it releases a great amount of energy that produce electricity or even nuclear explosion.

➢ Weak nuclear force is another type of nuclear force which:

• holds particles within protons and neutrons together.

• in neutron, the weak force is easily overcome. When neutrons decay, they form a new atom. Nuclei that decay in this way are called radioactive. 

5. Frictional Force

➢ Friction is a force that opposes motion between two surfaces touching each other. It causes the object that moves along the surface to slow down and eventually stop.

➢ It can be observed when you move a table or chair without wheels. You can

hardly move them because of friction between the foot of a furniture and the

floor.

➢ It also affects falling objects. When you drop a coin and a feather at the same time, both objects respond to gravity. However, the coin reached the ground first because air friction affects the feather. When objects move through air, the motion is opposed by friction.

➢ Air friction affects the motion of falling objects by acting against the force of gravity.

6. Centrifugal and Centripetal Force

➢ Centripetal Force is a force that pulls an object inward. It is the force that pulls the object towards the center.

➢ Centrifugal force is an outward force that pulls an object away from the center. 

Directions: Let us do the activity on Observing Kinds of Forces

What you need:

• coin • feather • meter stick

What you need to do:

1. Get a coin. Throw the coin upward. Observe what happens.

2. Slide the coin on the floor. Infer why the coin slows down and stops.

3. Prepare a feather and a coin. Hold the feather and the coin 2 meters above the floor or ground. Observe which one will reach the ground first if you drop the feather and the coin at the same time.  

What have you found out?

1. Which object reached the ground first?

__________________________________________________________

2. What kind of force causes the coin to fall? Describe it.

__________________________________________________________

3. Why did the coin rolling on the floor slows down and stop?

__________________________________________________________

4. What kind of force opposes the motion of the feather?

__________________________________________________________

Let us summarize the lesson!

1. There are four forces which are called universal forces. These forces are

gravitational, magnetic, electric, and strong and weak nuclear force.

2. Gravitational Force is a force that pulls objects towards one another.

3. Magnetic Force is a force that causes objects to attract or repel each other.

4. Electric Force is the force that exist between charged particles. Objects with different charges attract each other, and objects with the same charge repel each other.

5. Nuclear Force is the force that holds the particles in the nucleus together.