About Midterm Exam 1 • When and where – Thurs Feb. 17 th 5:45-7:00 pm – Rooms: See course webpage. Be sure report to your TA’s room – Your TA will give a review during the discussion session next week. • Format – Closed book, 20 multiple-choices questions (consult with practice exam) – 1page 8x11 formula sheet allowed, must be self prepared, no photo copying/download-printing of solutions, lecture slides, etc. – Bring a calculator (but no computer). Only basic calculation functionality can be used. Bring a 2B pencil for Scantron. – Fill in your ID and section # ! • Special requests: – Email me at [email protected], w/ valid excuse for approval. – One alternative exam: 3:30pm – 4:45pm, Thurs Feb.17, in our 201 lab rm. Newton’s Laws Today: The 3 rd Law; and applications
About Midterm Exam 1. Lect. 8, Chapter 4: Newton’s Laws Today: The 3 rd Law; and applications. When and where Thurs Feb. 17 th 5:45-7:00 pm Rooms: See course webpage. Be sure report to your TA’s room Your TA will give a review during the discussion session next week. Format - PowerPoint PPT Presentation
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About Midterm Exam 1• When and where
– Thurs Feb. 17th 5:45-7:00 pm– Rooms: See course webpage. Be sure report to your TA’s room – Your TA will give a review during the discussion session next week.
• Format– Closed book, 20 multiple-choices questions (consult with practice exam)– 1page 8x11 formula sheet allowed, must be self prepared, no photo
copying/download-printing of solutions, lecture slides, etc.– Bring a calculator (but no computer). Only basic calculation functionality can be used. Bring a 2B pencil for Scantron.– Fill in your ID and section # !
• Special requests: – Email me at [email protected], w/ valid excuse for approval.– One alternative exam: 3:30pm – 4:45pm, Thurs Feb.17, in our 201 lab rm.
Lect. 8, Chapter 4: Newton’s LawsToday: The 3rd Law; and applications
Consider a person standing in an elevator that is accelerating upward. The upward normal force N exerted by the elevator floor on the person is
a) larger than
b) identical to
c) less than
the downward weight W of the person.
Person is accelerating upwards - net upwards force is non zero
N – mg = ma mg
N
Question 2
Newton’s Third Law For every action, there is an equal and opposite reaction.
• Finger pushes on box • Ffingerbox = force exerted on box by finger
Ffingerbox
Fboxfinger • Box pushes on finger• Fboxfinger = force exerted on finger by box
• Third Law: Fboxfinger = - Ffingerbox
Newton’s Third Law… FFA ,B = - FFB ,A. is true for all types of forces
Whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the one it exerts – either stationary or in motion.
FFw,m FFm,w
FFf,m
FFm,f
Gravity Fm,f = -mg
System of Interest
f - All forces opposing the motion
System 1: Acceleration of the professor and the cart
System 2: Force the professor exerts on the cart
Newton’s second law, combined with third law, applies to every system of interest.