Bell Work A bag of baseballs is suspended motionless from the ceiling by two ropes. Draw the Free Body Diagram of the bag and label all the forces A pebble is free-falling from the roof of a tall building. The wind is blowing westward. If there is air resistance, draw the possible scenario in a Free Body Diagram.

Forces Part 2: Laws of Motion Seo Physics

Net Force What is a Net Force? Σ = Sigma Total or Overall Forces in the object Fnet = F1 + F2 + F3 + ….. Σ = Sigma ΣF mean the sum of or Net force If equal = BALANCED If NOT equal = UNBALANCED

Net Force Practice 1 Top - Bottom Upward Force of 50 N Downward Force of 50 N Net Force is Fnet = Top Force – Bottom Force Fnet= 50 N – 50 N Fnet = 0 N OR ΣF= 0 N Top and Bottom are Equal BALANCED

DIY 1 Top - Bottom Upward Force of 80 N Downward Force of 20 N Net Force is Fnet = Top Force – Bottom Force Fnet= 80 N – 20 N Fnet = 60 N OR ΣF= 60 N Top Force is greater than the Bottom Force UNBALANCED

Net Force Practice 2 Right - Left Rightward Force of 30 N Leftward Force of 30 N Net Force is Fnet = Right Force – Left Force Fnet= 30 N – 30 N Fnet = 0 N OR ΣF= 0 N Right and Left are Equal BALANCED

DIY 2 Right - Left Rightward Force of 30 N Leftward Force of 80 N Net Force is Fnet = Right Force – Left Force Fnet= 30 N – 80 N Fnet = -50 N OR ΣF= -50 N Left Force is greater than the Right Force UNBALANCED

Newton’s Three Laws of Motion

1st Law of Motion (Inertia) What is Inertia? Object’s resistance to move What is the 1st Law? An object at rest will stay at rest An object in motion will stay in motion, unless acted upon by an outside force EX). Your notebook is not going to move unless you push it

2nd Law What is the 2nd Law? Units? Force is equal to mass multiplied by acceleration Equation? F = m*a (Force = mass * acceleration) Units? (N) = (kg) * (m/s2)

2nd Law Practice How much force is needed to accelerate a 1520 kilogram car 3 m/s2?

DIY 1. What acceleration will result when a 12 N net force applied to a 3 kg object? SOLN: 12 N = 3 kg x a a= 4 m/s2   2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. SOLN: 16 N =m x 5 m/s2 m= 3.2 kg 3. How much force is needed to accelerate a 66 kg skier 1 m/s2? ANS: 66 kg*m/s2 or 66 N 4. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/s2? ANS: -9800 kg*m/s2 or 9800 N downward direction

3rd Law What is the 3rd Law? For every action, there is an equal and opposite reaction Force EX). If I push the wall with a Force, the wall will push me back with an equal Force

Net Forces w/ 2nd Law Practice Fnet= m*anet OR ΣF= m* a a=9.8 m/s2 , unless given a different value EX). Find the mass of the hanging object (Ftension- Fg)=m*a (80 N-30 N)=m*a (50 N)= m*(9.8 m/s2) m= (50N)/(9.8 m/s2) m= 5.10 kg

DIY Smiley is rolling at an acceleration of 5 m/s2. If it has a mass of 2 kg, find the Force of push Fnet= m*anet OR ΣF= m* a (Fpush- Ffr)=m*a (Fpush - 80N)=(2 kg)*(5 m/s2) (Fpush – 80N)= 10 kg*m/s2 (Fpush – 80N)= 10 N Fpush =90 N \

2nd Law – Force equals mass times acceleration (F= m*a) Summary 1st Law – An object at rest will stay at rest, and an object in motion unless acted upon by an unbalanced force. 2nd Law – Force equals mass times acceleration (F= m*a) 3rd Law – For every action there is an equal and opposite reaction Force