Warm Up If the sum of all forces

Warm Up If the sum of all forces on a system add to zero (∑=0 N), the system is said to be in _____. If ∑=0 N for a system, what is true about the object’s 1. 2. a. b. c. Acceleration Velocity Position

Warm Up If the sum of all forces on a system add to zero (∑=0 N), the system is said to be in equilibrium. If ∑=0 N for a system, what is true about the object’s 1. 2. a. b. c. Acceleration – it is zero. If there are no net forces, there is no acceleration. Velocity – It is constant – it could be zero or positive or negative, but it is not changing Position – we don’t know – it could be moving or still

What is a free-body force diagram? Free body diagram = A diagram of an object that shows the size and direction of all forces acting on it Force is a vector quantity Therefore, the effect of a force depends on its magnitude and direction Draw forces as arrows, where the arrow length corresponds to magnitude

Types of Forces Gravity - Fg Surface - FN (normal) Applied Fa Friction - Ff air resistance - Fair Tension (hanging object) - Ft

Forces Contact Forces – forces through objects touching Non-contact forces – forces without touching � Gravity � Magnetism � Electrostatic

Draw the free-body diagram of a soccer ball being kicked What are the forces on the soccer ball? Which way should the forces be drawn?

Draw the free-body diagram of a soccer ball being kicked What are the forces on the soccer ball? Which way should the forces be drawn? FN Ff Force of Ground (Normal Force) Force of Kick FA FG Force of Gravity

FBD of a ball in the air Which direction is the ball moving? ? WE DON’T KNOW! Could be up, down, left, right-we just know that the ball is accelerating downwards

Mass vs Weight Mass – how much matter is in an object (kg) Weight = Fg – force of gravity on an object � Fg = m*9. 8 m/s/s

FBD white board practice 1. Start by filling in mass and Fg using � Fg=m*9. 8 m/s 2 2. Set up Fnet mathematical expression � Fnet as sum (or difference) of your overall forces � Solve for unknowns

Newton’s Second Law The acceleration of an object is proportional to the unbalanced force on an object, and inversely proportional to its mass Fnet = m*a Net Force = mass * acceleration Units: N = kg * m/s 2

FBD white board practice 1. Start by filling in mass and Fg using � Fg=m*9. 8 m/s 2 2. Set up Fnet mathematical expression � Fnet as sum (or difference) of your overall forces � Solve for unknowns 2 b. Set up Fnet mathematical expression Fnet = ma