Homework (Due Wednesday)In Lab • Page 66 Review Questions #’s 2, 4, 6-11, 13-16, 18-20 • Do Now!!! • How long does it take for a ball to hit the ground from a balcony 15m high?
Chapter 6.4: Action and Reaction on Different Masses Consider the recoil of a rifle…
Chapter 6.4: Action and Reaction on Different Masses Consider a cannon and cannon ball… The shuttle continually recoils against the expelled gas from the rockets. No atmosphere is needed for this interaction.
Chapter 6.5: Do Action and Reaction Forces Cancel? It depends on context…
Chapter 6.6: The Rickshaw Problem Pull of man on rickshaw Pull of rickshaw on man Friction b/w cart wheels and ground Push of ground on man Push of man on ground Acceleration is due to net force
Chapter 6.6: The Rickshaw Problem Net force on the rickshaw? Pull of man – friction of wheels on ground Net force on the man? Push of ground on man - Pull of rickshaw on man Net force on the ground? Push of man on ground – friction of ground on wheels
Consider the following three examples. The action force is stated; determine the reaction force. Use the pop-up menu to view the answer. Athlete pushes bar upwards. Bowling ball pushes pin rightwards. Compressed air pushes balloon wall outwards.
Check Your Understanding1. Consider the interaction depicted below between foot A, ball B, and foot C. The three objects interact simultaneously (at the same time). Identify the two pairs of action-reaction forces. Use the notation "foot A", "foot C", and "ball B" in your statements. Answer Fa on b is equal and opposite to Fb on a Fc on b is equal and opposite to Fb on c
. Identify at least five pairs of action-reaction forces in the following diagram. F man feet on ground F ground on man’s feet F man’s hand on left side of rope F of left side of rope on man’s hands F of monkey pulling to right on rope F of rope pulling left on monkey F of monkey pulling left on rope F of rope pulling right on monkey F of rope pulling left on tree F of tree pulling right on monkey
Good Practice Problems) • A high diver jumps off a high platform. You time him with your watch and it takes 2.4s for the diver to hit the water. A) How high is the platform? B) How fast is the diver going the instant before he hits the water? • John stubs his toe on the coffee table with a force of 100N. A) What is the acceleration of John’s 1.80kg foot? B) What is the acceleration of the table if it has a mass of 20.0kg? • What is the minimal force a mother must exert to lift her 5.0kg baby straight up out of its crib? • A common malady in runners who run on too hard a surface is shin splints. If a runner’s 7kg leg hits the pavement so that it comes to rest with an acceleration of -200.00m/s2 on each hit, how much force must the runner’s leg withstand on each step? • In the district soccer championship finals, Elizabeth kicks a 0.600kg soccer ball with a force of 80.0N. How much does she accelerate the soccer ball
Do now!!! • A car (5000kg) collides with a truck (10000kg) causing the car to slow down at a rate of 7m/s2. What is the acceleration of the truck?