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Exam 1: Chapters 1-4 60% Problems – one problem from WebAssign with different numbers Understand homework problems Review notes and text Try new problems 40% Multiple Choice Questions Review Power Points (on web page) Review Before Class Assignments Try Questions

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• Exam 1: Chapters 1-4

• 60% Problems – one problem from WebAssign with different numbers

• Understand homework problems

• Review notes and text

• Try new problems

• 40% Multiple Choice Questions

• Review Power Points (on web page)

• Review Before Class Assignments

• Try Questions

• Graphs, Pictures and Drawings (Sketches)

• Don’t rely on memorized equations

5-1a Force – a push or pull.

• CT1: The force of the elevator on Norbert and Zot is

• up.

• down.

Assume the elevator is near the Earth’s surface and that it is right-side up in the cartoon.

• CT2: The force of the non-sticky elevator surface on Norbert and Zot is

• up.

• down.

Assume the elevator is near the Earth’s surface and that it is right-side up in the cartoon.

• CT3: The acceleration of Norbert and Zot is

• up.

• down.

• zero

Fig. 5.1, p.113 it is right-side up in the cartoon.

5-1 B. Mass it is right-side up in the cartoon.

The mass of an object is the amount of matter (stuff) in that object. It is the same for a given object everywhere in the Universe. Mass is also called inertia because it resists being moved.

5-2 Newton’s First Law: it is right-side up in the cartoon. A body remains in uniform motion (or at rest) unless acted upon by a net external force.

• acceleration due to Earth’s rotation  0.03 m/s2

• acceleration due to Earth’s orbit  0.006 m/s2

• acceleration due to Sun’s orbit  2 x 10-10 m/s2

An inertia frame of reference is a coordinate system (or frame) in which Newton’s Law’s hold.

We will assume that the Earth’s surface is an inertial frame and not make errors greater than 0.03/10 = 0.3%.

A. it is right-side up in the cartoon.

B.

C.

D.

E.

CT4

A. it is right-side up in the cartoon.

B.

C.

D.

E.

CT5

5-3 Newton’s Second Law: it is right-side up in the cartoon. The net external force is equal to the mass times the acceleration.

F = ma

Force and acceleration are vectors

• Fx = max

• Fy = may remember Galileo!

• Fz = maz

Normally we will do problems in a plane with only x and y components.

Calibrating a it is right-side up in the cartoon.“Force Meter”

Experiments show forces add as vectors.

Acceleration is Proportional to Force it is right-side up in the cartoon.

Acceleration is Inversely Proportional to Mass it is right-side up in the cartoon.

Applications of Newton’s Laws - Method it is right-side up in the cartoon.

• Draw picture of the problem.

• Choose body (bodies) to isolate.

• Draw Free Body Diagrams (FBDs) for isolated bodies.

• Choose and label coordinate axes.

• Apply Newton’s 2nd Law: Fx = max and Fy = may

• Solve for F, m or a.

• Work out kinematics.

• Check solution is reasonable.

P5.6 (p.136)

• Concept Question 6 it is right-side up in the cartoon.

• P5.6b: If the parachutist comes to rest over a shorter distance, the force exerted by the ground will be

• greater.

• less.

• the same.

F it is right-side up in the cartoon.AB

A

B

FBA

5-4 Newton’s Third Law: If body A acts on body B, then body B acts back on body A with a force equal in magnitude but opposite in direction.

FAB and FBA are 3rd Law pairs.

CT7 it is right-side up in the cartoon.

A.

B.

C.

D.

E.

P5.18 it is right-side up in the cartoon.

(p.137)

• Concept Question 8

• P5.18b: If the 5 N force is applied to the heavy box instead, the contact force between the boxes will be

• greater.

• less.

• the same.

5-5 The Vector Nature of Forces it is right-side up in the cartoon.

Two Astronauts Pushing a Satellite with Forces that Differ in Magnitude and Direction

P5.22 (p.137) it is right-side up in the cartoon.

P5.28 (p.138) it is right-side up in the cartoon.

Orbit of Moon about the Sun it is right-side up in the cartoon.

Actual

Exaggerated and incorrect

y it is right-side up in the cartoon.

x

5-6 Gravitational Force or Weight

Fg = mg (weight)

g = -9.81 j (m/s2 )

Apparent Weight is the force you actually feel pushing on you – often the floor.

P5.35 (p.138) it is right-side up in the cartoon.

• Concept Question 9 it is right-side up in the cartoon.

• P5.35b: If the constant speed of descent is greater than 1.1 m/s, the force of air resistance is

• greater.

• less.

• the same.

• Concept Question 10 it is right-side up in the cartoon.

• P5.33a: Your normal weight is 610 N and the scale in the elevator reads 720 N. The acceleration of the elevator

• upward.

• downward.

• zero.

• Concept Question 11 it is right-side up in the cartoon.

• P5.33c: Your normal weight is 610 N and the scale in the elevator reads 720 N. The magnitude of the velocity of the elevator is

• increasing.

• decreasing.

• zero.

5-7 Normal Forces it is right-side up in the cartoon.The Normal Force May Equal the Weight

The Normal Force it is right-side up in the cartoon.May Differ from the Weight

An Object on an Inclined Surface it is right-side up in the cartoon.

P5.42 (p.138)

• Concept Question 12 it is right-side up in the cartoon.

• P5.42b: If the angle of the incline is decreased, the normal force will

• increase.

• decrease.

• stay the same.

A. it is right-side up in the cartoon.

B.

CT13