Newton's Laws of Motion Slide 4-19 Newton 0th Law Objects are dumb - They have no memory of the past and cannot predict the future. Objects only know what is acting directly on them right now Newton's 1st Law An object that is at rest will remain at rest and an object that is moving will continue to move in a straight line with constant speed, if and only if the sum of the forces acting on that object is zero. Newton's 2nd Law acceleration of an object = sum of forces acting on that object / the mass of the object Newton's 3rd Law Recall that a force is an interaction between two objects. If object A exerts a force on object B then object B exerts a force on object that is in the opposite direction, equal in magnitude, and of the same type.

Forces and Two Books Slide 4-19 A.Draw a Force Diagram for each book B.What type of force does the upper book exert on the lower book? (e.g., frictional, gravitational, etc.) C.Rank the forces in the two force diagrams from largest to smallest

Scales and Elevators (Apparent Weight) Slide 4-19 Suppose a person with a mass of 60 kg is in an elevator standing on a scale. Use a system schema and free body diagrams of the scale and the person to determine what the scale would read for the following situations: A. If the elevator is descending at 4.9 m/s. B. If the elevator has a downward acceleration of 4.9 m/s/s. C. If the elevator has an upward acceleration of 4.9 m/s/s.

Half Atwood-Machine (Working with Systems) Slide 4-19 A block of mass M 1 is sitting on a frictionless table. It is connected by a massless string over a massless and frictionless pulley to another block of mass M 2. (a) Build free-body diagrams for each of the masses and write equations of motion for each object. Use the coordinate x 1 shown in the figure for the position of mass M 1 and coordinate y 2 shown in the figure for the position of mass M 2. (b) Use these equations of motion to obtain the acceleration of the two objects. Explicitly state any conditions that you are applying to solve the equations.

Parking on a Hill Slide 4-19 A.If you park on a hill with a 10 degree slope with the car held by the parking brake, what is the magnitude of the frictional force that holds your car in place? (Work in symbols) B.The coefficient of static friction between your car's wheels and the road when wet is What is the largest angle slope on which you can park your car in the rain so that it will not slide down the hill? C.The coefficient of kinetic friction between your wheels and the wet road surface is If someone gave your your car a push on the wet hill and it started sliding down, what would its acceleration be?