Forces of Motion

Force A force is a push or pull exerted on an object in order to change the motion of an object Force has two things –Strength –Direction

Units Force is measured in something called Newtons –Named after Isaac Newton –Are in units of kg (m/s^2) Kg = Mass m/s^2 = Acceleration Force = Mass x Acceleration

Net Force Net Force is simply the combination of all the forces acting on an object Ex) Two guys try to move a piano. One guy is pulling with a force of 30 Newtons and another guy is pushing with a force of 24 Newtons. What is the net force on the piano? 24 N 30 N =

Net Force A guy is trying to push a desk across a carpet floor. He is pushing with a force of 35 Newtons and the carpet’s friction is slowing it down with a force 9 Newtons. What is the net force? 35 N 9 N =

Balanced Forces Balanced Forces are when the forces on an object produce a net force of 0 Newtons. In other words the balanced forces will not cause a change in the motion of a moving object or make a non-moving object start moving

Unbalanced Forces When the net force on an object is not 0 Newtons, the forces on the object are said to be unbalanced. Unbalanced forces cause a change in the motion of an object and are necessary to get an object to start moving

Balanced and Unbalanced Forces If two teams of people are playing tug of war and each team is pulling the rope with a force of 12 Newtons. Is the rope balanced? What is the net force?

Balanced and Unbalanced Forces What if there is an elevator of people with a force of 195 Newtons pulling down and a tension force of 317 Newtons pulling up. Is the Elevator balanced? What is the net force?

Types of Forces There are several types of forces of motion –Some increase motion –Some oppose motion

Friction Friction is a force that opposes motion between two surfaces that are in contact Examples include –Rubbing hands together –Pushing a heavy object over a rough surface –Pouring sand on ice

Gravity A force of attraction between objects due to their masses We consider gravity a downward force on Earth, since everything is pulled toward its center

Buoyancy Buoyancy is the force that pushes objects that are less dense than water upward Example –Ships –Person in water –Block of wood –Inner tube

Tension Tension is the pulling force applied to a rope or a spring that attempts to stretch it out

Tension If you walk your pet, you would use a leash or a rope. There would be a tension force in the rope if it was trying to walk faster than you Ex) Your pet pig pulls you down the street with a force of 12 Newtons

Magnetism A magnetic force is found between two magnets The magnetic force can be repulsive or attractive –Attractive force = a positive end and a negative end –Repulsive force = two positive ends or two negative ends

Magnetic Force Each magnet has a positive and negative end. Opposites attract, Same repels

Normal Force Normal Force is the force of an object pushing back against an object pushing on it. Ex) Person on a chair Book on a desk Box on the ground

The End