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Transcript of Forces!
By - Crockett, Ezio, Isaac, Rachel. Forces! What is a force? What is Net Force? Newton's First Law
Law of Inertia - Force is an action put upon an object that changes the current state of the object. What are the units used
to measure force? The units used to measure force include newtons, dynes, kilogram-force, pound-force, and poundals. Net force is the amount of force acting against an object. - When an object has force put upon it, a change made to the object could be in movement, direction, or construction. - Force can also be thought of as a push or pull of an object resulting in the effect an object has on other objects. Newtons are equivalent to the amount of net force used to move an object at a certain velocity. Newtons are equal to the mass of an object moving at a certain speed. (kilograms x m/s squared) Newtons are the most common unit used. Dynes are equivalent to 10 micronewtons. Kilogram force is equal to 9.80665 Newtons. Pound force is the amount of gravitational force based on the mass of an object. Poundals are the force needed to accelerate a 1 pound-mass object. The environment and the restrictions around the object are components that affect the net force. i.e. If wind was contributing to moving the object, the net force would be greater. Free Body Diagrams A free body diagram is often a sketch of the components and different objects that may have force. A free body diagram normally has arrows noting the different amounts of net force on an object. This shows the movement and direction the object would go in. A free body diagram is used to easily see the unknown forces on the object and the motion the object would move in. Car Free Body Diagram Example The car is going down a hill so the gravity pull towards the ground is making it move quickly down slope. The different kinds of forces
in our universe Gravity: An attractive long range force between objects with mass.
Electromagnetic force: An attractive or repulsive long range force between two objects with charge.
Strong Nuclear force: An attractive short range force between particles like protons and neutrons
Weak Nuclear force: A short range force responsible for beta decay. As well as an initiator for the process of hydrogen fusion in stars.
Normal Force: A force between an object that is perpendicular to its surface.
Tension Force: A force that is caused during suspension. Motion based on Net Force When an apple fell onto Isaac Newton's head he realized that something created a pull, causing the apple to smack him right on the top of his head. The mass of the apple and the gravitational pull towards the earth resulted in the apple falling. From this a conclusion has been established that all objects have a pull towards earth that results in movement of the object. This "something" was established as gravity .. Gravity is a crucial physical force that is responsible for interactions which occur because of mass between particles As the car rolls down the slope, the momentum of the car will speed up because with the force of gravity pushing down combined with mass of the car and the slope of the ground makes the wheels of the car to spin quicker and quicker. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. The arrows in the free body diagram show the different amounts of net force put onto the car. Runner Free Body Diagram Example This is a picture of a man running. There are 4 different forces being put on the man; air resistance, friction, gravity, and ground reaction force. Air resistance, sometimes called drag, is a resisting force against a solid object moving. Friction is the force that resists relative motion of two solid surfaces in contact. Gravitational force is the force of gravity that is directed downwards. The force of gravity is always equivalent to the weight of the object. Ground reaction force is the force exerted by the ground on a body in contact with it. If the air resistance is -10N, the body weight is
-600N, the friction is 100N and the ground reaction force is 700N, then the resultant net force is 100²+90²= 134.5² . DEMONSTRATION! If the mass of the car is -300N, the air
resistance is -100N, the friction is 10N, the ground reaction force is 200N, the resultant net force is -100²+-90² = -134.5² N. The slope of the ground will affect the direction and acceleration of the car because the vertical force is canceled by the mass, but the horizontal component keeps the car moving. Mass A.R. Friction G.R.F. Skier Free Body Diagram Example This is the picture of a skier going down a slope. The arrows shown are the forces pushing on the skier. Friction, gravity, air resistance, and ground reaction are the forces pushing on the skier. If the skier's mass is -200N, the air resistance is -100N, the friction is 200N, and the ground reaction force is 300N, the resultant net force would be 100²+100²=141². Force is an interaction between two objects - How this connects to Newton's 1st law - What is happening Thank you for watching our presentation! Any questions, comments, feedback? net force = mass X acceleration acceleration = net force / mass As net force increase the acceleration increases