1. WHAT IS FORCE?
Look at the pictures below. How’s force applied in each picture?
2. WHAT IS FORCE?
FORCE- is any kind of push or pull acting upon an object as a result of
its interaction with another object
-helps us in our daily activities
-exerted on one object by another
-force is not visible, but we can sense it because we see its effect on
objects
● Whenever there is an interaction between 2 objects, there is a force
upon each each of the objects. When the interaction ceases(stops),
the 2 objects no longer experience the force. Force only exist as a
result of an interaction.
3. ALL ABOUT FORCE
*FORCE is measured in Newton ( N)-a unit named in honor of Sir Isaac
Newton who discovered gravity and formulated principles related to force
and motion.According to him, an object will move only if there is a net
force acting upon it.
*Net Force- is the total amount of all the forces acting on an object
-If the object has two unequal forces acting on it, the net force will be
unbalanced
4. SOME EXAMPLES WHEREIN FORCES ARE APPLIED
PROPERLY
1. Playing sports that require hitting balls in a
controlled manner, such as soccer, volleyball,
basketball, or baseball
2. Pulling objects to prevent them from falling or
sinking
3. Pushing objects to transport them from one place
to another
5. KINDS OF FORCES
1. CONTACT FORCES- these are forces that result
from physical interaction
Ex. frictional force, tension force, and muscular force
6. EXAMPLES OF CONTACT FORCES
TENSION FORCE- it is the force exerted by a rope,
cable, chain
8. EXAMPLES OF CONTACT FORCES
FRICTION- is the force that acts opposite the
direction of motion
-prevents us from slipping
9. EXAMPLES OF CONTACT FORCES
MUSCULAR FORCE- is the force exerted by using body parts such as
the arms or legs. It is a force produced by muscle action and is a
contact force because there is contact between the surfaces. Every
movement of the body necessitates the use of muscular force.
10. KINDS OF FORCES
2. NONCONTACT FORCES/DISTANCE FORCES-
these are forces that act within a certain distance
Ex. magnetic force, gravitational force
11. EXAMPLES OF NON CONTACT FORCES
MAGNETIC FORCE- is produced between two electrically
charged moving particles
-found between two magnets or between a magnet and a
magnetic material
12. EXAMPLES OF NON CONTACT FORCES
GRAVITATIONAL FORCE- is the force of attraction that
keeps bodies in the universe together
-Examples- earth is being attracted to the sun-since the sun
has a greater mass-earth is attracted to it and revolves
around it
13. FORCES CAN BE CLASSIFIED INTO:
1. BALANCED FORCES- are two equal forces acting on an
object in opposite directions
-when forces are balance, the object either stays at rest
or continues to move at the same speed and at the same
direction
-balanced forces are present in hanging, floating,
standing, or sitting objects
15. FORCES CAN BE CLASSIFIED INTO:
2. UNBALANCED FORCES- are two unequal forces acting
on an object
-make the object speed up, slow down, change direction,
remain in place, or change in shape
16. FORCES CAN BE CLASSIFIED INTO:
UNBALANCED FORCES- are two unequal forces acting on
an object
17. LET’S WATCH THESE VIDEOS!
https://www.youtube.com/watch?v=SybIX2nEn1E
https://www.youtube.com/watch?v=eTuiLNYz7JM
https://www.youtube.com/watch?v=nk35aGqJ-F8
https://www.youtube.com/watch?v=kUVZIRz7PKs
Editor's Notes
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
Whenever you get up from your bed, lift your bag, and go up using the stairs, elevator, or escalator, you overcome gravity. You also beat gravity for a while when you jump off the ground. All these movements involve the use of force. In lifting objects, tension force is needed.Pulleys are used to lift heavy objects. The tension in the rope transfers our force applied in the downward or horizontal direction to lift the object in the upward direction. If the object is hanging by a cord, the tension in the cord is just equal to the load’s weight. To lift the load up, a tension force greater than the load’s weight is needed. To start moving an object up, lifting force greater than the object’s weight is needed. In case of hanging objects, the lifting force is the tension in the rope, chain, or strap. For objects supported on a solid surface, as in an elevator, the lifting force is also a normal force.
Ropes and cables are useful for exerting forces since they can efficiently transfer a force over a significant distance (e.g. the length of the rope). For instance, a sled can be pulled by a team of Siberian Huskies with ropes secured to them which lets the dogs run with a larger range of motion compared to requiring the Huskies to push on the back surface of the sled from behind using the normal force. (Yes, that would be the most pathetic dog sled team ever.)
It's important to note here that tension is a pulling force since ropes simply can't push effectively. Trying to push with a rope causes the rope to go slack and lose the tension that allowed it to pull in the first place. This might sound obvious, but when it comes time to draw the forces acting on an object, people often draw the force of tension going in the wrong direction so remember that tension can only pull on an object.
Things hanging on chains, cords or ropes are supported by tension force.
Jumping up requires that you push hard on the floor or ground with your feet and. As nature designed it, the floor or ground exerts a reaction force on you. This reaction force will have to be greater than your weight for you to get off from the ground. Where will it be easier to jump higher for a volleyball spike, on a hard wood court or on the beach? Why? How does the softness or hardness of the floor affect the jump?
Jumping up requires that you push hard on the floor or ground with your feet and. As nature designed it, the floor or ground exerts a reaction force on you. This reaction force will have to be greater than your weight for you to get off from the ground. Where will it be easier to jump higher for a volleyball spike, on a hard wood court or on the beach? Why? How does the softness or hardness of the floor affect the jump?
We learned in the previous lesson that gravity makes everything fall down. If this is the case, then why are not you falling off your chair to the floor even while Earth’s gravity is pulling you down? While you are seated, your chair is exerting an upward force on you, just enough to support your weight. This support force is also called normal force.
Now that you have understood the forces needed in lifting things and jumping off the ground, you are ready to understand how forces can make things fly. What are the forces on an airplane that is already flying at a constant altitude? To keep the plane from falling, there has to be an upward force on it to cancel out Earth’s downward pull. This upward force is called the lift. The lift is exerted by the air moving under the plane’s wings. As shown above, there is just enough lift to carry the airplane’s weight. If the pilot needs to bring the plane higher, he will need to get more lift on the wings. To lower the plane, the lift will have to be reduced. This is achieved by moving the flaps on the wings of the plane. Now, can you explain how an airplane on the ground can take off from the runway?
The airplane’s engines are designed to give it a forward push, also called the THRUST. However, this thrust is horizontal, and does not lift the plane. While the airplane speeds up moving forward, air passes both above and below the wings. The shape of the wings causes air to pass faster above than below the wings. This causes the pressure below the wings to be greater than that above the wings. This difference creates the lift force. Airplanes do not take off vertically, helicopters do. Choppers do it by having its wings-long blades attached to its motor-rotate very fast to create the needed lift.
The airplane’s engines are designed to give it a forward push, also called the THRUST. However, this thrust is horizontal, and does not lift the plane. While the airplane speeds up moving forward, air passes both above and below the wings. The shape of the wings causes air to pass faster above than below the wings. This causes the pressure below the wings to be greater than that above the wings. This difference creates the lift force. Airplanes do not take off vertically, helicopters do. Choppers do it by having its wings-long blades attached to its motor-rotate very fast to create the needed lift.
The airplane’s engines are designed to give it a forward push, also called the THRUST. However, this thrust is horizontal, and does not lift the plane. While the airplane speeds up moving forward, air passes both above and below the wings. The shape of the wings causes air to pass faster above than below the wings. This causes the pressure below the wings to be greater than that above the wings. This difference creates the lift force. Airplanes do not take off vertically, helicopters do. Choppers do it by having its wings-long blades attached to its motor-rotate very fast to create the needed lift.
The airplane’s engines are designed to give it a forward push, also called the THRUST. However, this thrust is horizontal, and does not lift the plane. While the airplane speeds up moving forward, air passes both above and below the wings. The shape of the wings causes air to pass faster above than below the wings. This causes the pressure below the wings to be greater than that above the wings. This difference creates the lift force. Airplanes do not take off vertically, helicopters do. Choppers do it by having its wings-long blades attached to its motor-rotate very fast to create the needed lift.
The airplane’s engines are designed to give it a forward push, also called the THRUST. However, this thrust is horizontal, and does not lift the plane. While the airplane speeds up moving forward, air passes both above and below the wings. The shape of the wings causes air to pass faster above than below the wings. This causes the pressure below the wings to be greater than that above the wings. This difference creates the lift force. Airplanes do not take off vertically, helicopters do. Choppers do it by having its wings-long blades attached to its motor-rotate very fast to create the needed lift.
