Part 1: Conceptual Newton's Laws

• Define laws
• Conceptual Questions
  • If you were in a spaceship and fired a cannonball into space, how much force would have to be exerted on the ball to keep it moving once it has left the spaceship?
  • If an elephant were chasing you, its enormous mass would be most threatening. But if you zigzagged, its mass would be to your advantage. Why?
  • If suddenly the force of gravity of the sun stopped acting on the planets, in what kind of path would the planets move?
• Example of N3
  • Why does a cannon recoil when it fires a cannonball?
  • A person drops the ball which falls because the Earth pulls the ball down. What is the reaction force to that?
  • If a bicycle and a massive truck have a head-on collision, upon which vehicle is the impact force greater? Which vehicle undergoes the greater acceleration?
• Example of N2
  • An elevator (mass = 1000 kg) is supported by a single cable.
    • When the elevator is at rest, what is the tension in the cable?
    • The elevator starts to move upwards at 1m/s/s. Is the tension more, less, or the same?
    • When the elevator is ascending upward at a constant speed, is the tension more, less, or the same as (a)?
    • The elevator begins to slow as it reaches the proper floor. Is the tension more, less, or the same as (a)?
  • If a loaded truck can accelerate at four m/s/s and loses its load so it is only half as massive, what acceleration can it attain for the same driving force?
  • The force of gravity is twice as great on a 2-kg rock as on a 1-kg rock. Why then does the 2-kg rock not fall with twice the acceleration?

Part 2: Newton's Second Law Lab

• Review lab results
  • How does F affect a?
  • How does m affect a?
• For each lab, know the following:
  • How were we able to measure mass, force and acceleration?
  • How are the variables related? Are they directly or inversely proportional?
  • What did the data table look like?
  • What did the graph look like?
  • G23 ONLY: Be able to develop Newton's second law from the graph.

Part 3: Problems

• All Group (no angles)
  • A 50kg gymnast is hanging from the rings. If each of the gymnast's arms has a maximum strength of 200N, will it be enough to support their weight?
  • Three women push a stalled car. Each woman pushes with a 425N force. The force of friction is 800N. What is the mass of the car if the car accelerates at 0.85m/s/s?
• Standard/Accelerated (vector components)
  • Break up the following forces into horizontal and vertical components
    • 28.2N at an angle of 45
    • 150N at an angle of 53
  • Find the total strength of the force knowing its components:
    • Fx = 50N, Fy = 20N
    • Fx = 25N, Fy = 45N
  • A tavern sign weighing 200N is connected to two cables. One of the cables is fastened to the ceiling at 60 angle while the other is fastened directly horizontally to the left. What is the force on each cable?

• Consider a 12kg box being pushed along at a constant speed. The force of friction is 10N. The force pushing it along is directed downat an angle of 30 from the horizon. How strong is the force pushing the box? How strong is the support force