Determine the resultant for each group of vectors below: b) c)

Transcription

1 Determine the resultant for each group of vectors below: a) b) c)

2 a) Magnitude 11.7 Direction: 70 degrees North of East -3 7

3 b) Magnitude: 1 Direction: West

4 c) Magnitude: 7.8 Direction: 40 degrees East of South or 50 degrees South of East. 5

5 Quote of the Day Waiter, there's no fly in my soup. - Kermit the Frog

6 Daily Objective Students will identify the forces exerted on an object in order to create free-body diagrams.

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9 Contact Forces: Result from physical contact between two objects. Field Forces: Gravitation, electrical charges, magnetism

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13 Two people kick a soccer ball at the same time, one person from the west side of the ball, the other from the southeast side. Draw a free body diagram to represent just these two forces. If each person exerts a force of 10 N on the ball, what will be the net force on the ball? (Magnitude and Direction.)

14 The Process for Solving Equilibrium Problems

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18 Daily Objective

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21 An object in equilibrium is either: If the object is at equilibrium, then the net force acting upon the object should be 0 Newton. Thus, if all the forces are added together as vectors, then the resultant force (the vector sum) should be 0 Newton.

22 Quote of the Day If at first you don't succeed...

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24 The Process for Solving Equilibrium Problems

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26 1. A 10.0 kg mass hangs from two strings, each making an angle of 35.0 with the ceiling. What is the tension in each string? Solution

27 5. Find the tensions in strings 1 and 2 supporting a 20.0 N rock hanging from the ceiling. Strings 1 and 2 make angles of 30.0 and 40.0 with the ceiling, respectively. Solution

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29 Extra Practice

30 INERTIA A common misconception is that an object on which no force is acting will always be at rest. Ex. A block sliding on a perfectly smooth surface would slide forever in the absence of an applied force.

31 Inertia is the tendency of an object not to accelerate. Newton s first law is often referred to as the law of inertia because it states that in the absence of a net force, a body will preserve its state of motion. In other words, Newton s first law says that when the net external force on an object is zero, the object s acceleration (or the change in the object s velocity) is zero. Mass is a measure of inertia.

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33 Net Force is a single force whose external effects on a rigid body are the same as the effects of several actual forces acting on the body. It is the vector sum of all forces acting on an object.

34 Review of basic applications of F = ma from last year.

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40 Ans..5 m/s2

41 Quote of the Day The early bird may get the worm, but it's the second mouse that gets the cheese...

42 Daily Objective Students will identify action-reaction pairs in order to solve problems involving Newton's Third Law of Motion.

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44 The force of friction also depends on the composition and qualities of the surfaces in contact. For example, it is easier to push a desk across a tile floor than across a floor covered with carpet. The quantity that expresses the dependence of frictional forces on the particular surfaces in contact is called the coefficient of friction. The coefficient of friction is represented by the symbol μ, the lowercase Greek letter mu.

45 Friction force is always directed in the opposite direction to motion.

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47 A refrigerator is placed on a ramp. The refrigerator begins to slide when the ramp is raised to an angle of 34. What is the coefficient of static friction? (Ans..67 )

48 A student attaches a rope to a 20.0 kg box of books. He pulls with a force of 90.0 N at an angle of 30.0 with the horizontal. The coefficient of kinetic friction between the box and the sidewalk is Find the acceleration of the box.

49 2. A 15.0 kg block is at rest on a 40.0 incline. Find the magnitude of the normal force and the friction. Solution

50 Ans. a =.84 m/s2

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52 An alternative statement of this law is that for every action, there is an equal and opposite reaction

53 Ex. Hammer and Nail

54 Ex. The Earth and an asteroid.

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