Review for Test #3 Responsible for:

- Chapters 9 (except 9.8), 10, and 11 (except 11.9) - The spring (6.2, 7.3, 8.2-8.3)

- Problems worked in class, class notes - Homework assignments

Test format:- 13 problems, 11 simple, 1 intermediate, 1

advanced, 7.7 pts each - Time: 50 minutes only

Test materials: - Pencil, paper, eraser, and calculator

- No formulae sheet - Closed textbook and notes

Material Covered Chapter 9: Impulse and Momentum

- Impulse-momentum theorem- Conservation of Linear

momentum - 1 and 2D collisions- Center of mass

Chapter 10: Rotational Kinematics and Energy- , , , ar, and at

- Rotational kinematic equations- Rolling motion (tire)- Moment of inertia

- Rotational work and kinetic energy - Conservation of Energy with rotation

Example Problem

,

Grades returned by next Monday?

A 0.200-m bar with a mass of 0.750 kg is released from rest in the vertical position. A spring is

Chapter 11: Rotational Dynamics and Static Equilibrium - , =I

- Applications of =0, F=0- Center of gravity

- Angular momentum, conservation of ...

The Spring- Force due to a spring (Hooke’s Law)

- Work and potential energy of a spring

attached, initially unstrained, and has a spring constant of 25.0 N/m. Find the tangential speed with which the free end strikes the horizontal surface. (drawing to be provided)

Solution:

Bar rotating with axis at one end rotational KE, no translational KE

Bar falls from some height gravitional PE (Ug)

A spring is attached to bar spring PE (Us)

Bar rigid body need moment of inertia

Use Conservation of Energy

2

212

61

221

22

31

21

231

2212

21

,

,

0,0

,2

0,0

ftf

ft

f

fftfrod

fff

fgf

ii

ii

sgR

kxmE

kxL

mLE

LrmLIkxIE

Uy

mghEh

mgE

xUUKE

v

v

vv

yih since this would mean all mass of rod is at yi=h, but mass is distributed. So, take mass to be located at center of gravity

m 1236.01.01.02.0

?22

f

f

x

x From geometry of problem

Return to Conservation of Energy and solve for vt

m/s v

v

v

v

v

09.2528.188.5

)1236.0(750.0

0.253)20.0)(80.9(3

33

2

22

2

2

2212

61

2212

61

t

t

ft

ft

iftf

xm

kgL

kxL

mgm

Lmg

hmgEkxmE