2. Fyrsta skilyrði fyrir jafnvægi
Annað skilyrði fyrir jafnvægi

3. Skilgreining massamiðju!

5. Yfirlitstafla, glæra 1 K Yrðing Hvenær Dæmi Mótdæmi 3
v = v0 + a t o.s.frv.
Jöfn hröðun
Fall, skáborð, trissa
Fall í vökva
arad = v2/R
atan = d Iv I/dt
Hlutur á ferð
Hringhreyfing 4
Fnet = m a
Newton 2
Daglegt líf
(Einstein)
FA on B = - FB on A
Newton 3
Vagnhestur
Engin 5
fs < msn
Stöðunúningur
Velta
fk = mkn
Hreyfinúningur
Hlutur rennur
Velta, straumefni 6
W =  F.ds
Alltaf
Allir kraftar
W = F.s
F = fasti
F = m g
F = k/r2
W =  Fx dx
F = Fx
Einvíð hreyfing
Þrívíð hreyfing
Wtot = DK
Allt

6. Yfirlitstafla, glæra 2 K Yrðing Hvenær Dæmi Mótdæmi 6 P = F.v (afl)
Alltaf
Bíll
Engin 7
WAB(1) = WAB(2)
Kraftur geyminn
F = m g
F = - l v
$U: DU = -W
E = K + U
DE = 0
F = - grad U
Ef allir kraftar geymnir
U = m g y
U = ½ k x2
U = -GmM/r
Sama 8
p = m v
Alltaf, skilgreining
Fext = dP/dt
Newton
Daglegt líf
(Einstein)
P = fasti
Fext = 0
Árekstrar
K = fasti
Fjaðrandi árekstur
Billjarðkúlur, öreindir

7. Yfirlitstafla, glæra 3 K Yrðing Hvenær Dæmi Mótdæmi 8 J =  F dt = DP
Alltaf, skilgr.
Árekstrar
Engin
rCM = S mi ri/M
Skilgr.
Agnakerfi
(Einstein)
P = S pi = MvCM
Afleiðing
Sama
Fext=dP/dt =MaCM
Newton
P = MvCM = fasti
Fext = 0 10
K = KCM + Krot
Alltaf
Velta
KCM = ½ MvCM2
Hliðrun og snúningur

8. Yfirlitstafla, glæra 4 K Yrðing Hvenær Dæmi Mótdæmi 9 K = ½ Iw 2
Stjarfhlutur
Trissuhjól 10
Lz = Izw
Miðað við snúningsás
Nemandi á palli
Annar ás
text = dL/dt
Alltaf
Kraftapar á gjörð
Engin
t = Ia
Um fastan ás
Ás á hreyfingu
L = fasti
text = 0
Nemandi með lóð
Iiwi =Ifwf
I að breytast
Diskar

10. Example 11.1, síðu 408 Univ.Phys.

11. A 1-kg rock is suspended by a massless string from one end of a 1-m measuring stick. What is the mass of the measuring stick if it is balanced by a support force at the 0.25-m mark?
                                                            kg kg
3. 1 kg
4. 2 kg
5. impossible to determine

12. A 1-kg rock is suspended by a massless string from one end of a 1-m measuring stick. What is the mass of the measuring stick if it is balanced by a support force at the 0.25-m mark?
                                                            kg kg
3. 1 kg
4. 2 kg
5. impossible to determine

13. You decide to make yourself a desk, by attaching a wide shelf to the top of two legs. (A side view is shown.)
                                                           
When you put a book down on the end of the shelf, the force exerted ON the shelf at the attachment point labeled "A" is approximately
1. Upwards
2. Downwards
3. Rightwards
4. Leftwards
5. Zero

14. You decide to make yourself a desk, by attaching a wide shelf to the top of two legs. (A side view is shown.)
                                                           
When you put a book down on the end of the shelf, the force exerted ON the shelf at the attachment point labeled "A" is approximately
1. Upwards
2. Downwards
3. Rightwards
4. Leftwards
5. Zero
Ef hillunni væri ekki haldið niðri í þennan enda snerist hún!

15. You decide to make yourself a desk, by attaching a wide shelf to the top of two legs. (A side view is shown.)
                                                           
When you put a book down on the end of the shelf, the force exerted ON the shelf at the attachment point labeled “B" is approximately
1. Upwards
2. Downwards
3. Rightwards
4. Leftwards
5. Zero

16. You decide to make yourself a desk, by attaching a wide shelf to the top of two legs. (A side view is shown.)
                                                           
When you put a book down on the end of the shelf, the force exerted ON the shelf at the attachment point labeled “B" is approximately
1. Upwards
2. Downwards
3. Rightwards
4. Leftwards
5. Zero
Hvað héldi hillunni annars uppi? (Þyngd bókarinnar virkar niður,
í “A” er líka kraftur sem virkar niður.)

17. Example 11.3, síðu 411 Univ.Phys.

18. Spenna/Bjögun = Fjaðurstuðull

19. Togspenna
Togbjögun

20. Þjöppunarspenna
Þjöppunarbjögun

21. I-bjálki ! (léttur en sterkur)
Þjöppunarspenna
Togspenna
I-bjálki ! (léttur en sterkur)

22. Rýmisspenna
Rýmisbjögun

23. Rýmisspenna/Rýmisbjögun
Rýmisfjaðurstuðull

25. Skúfspenna/Skúfbjögun = Skúfstuðull

28. 1. Setup A is more likely to fail. 2. Setup B is more likely to fail.
A rock climber wants to set up a belay anchor to hang on. Compare the following two setups:
                                                       
(The top points are solid attachments to the rock, the loop at the bottom of the small slings is what the climber will hang off of. The slings are getting old, and could break if the tension in them is too large.)
1. Setup A is more likely to fail.
2. Setup B is more likely to fail.
3. The two setups are equivalent.

29. 1. Setup A is more likely to fail. 2. Setup B is more likely to fail.
A rock climber wants to set up a belay anchor to hang on. Compare the following two setups:
                                                       
(The top points are solid attachments to the rock, the loop at the bottom of the small slings is what the climber will hang off of. The slings are getting old, and could break if the tension in them is too large.)
1. Setup A is more likely to fail.
2. Setup B is more likely to fail.
3. The two setups are equivalent.
Togið er miklu meira!

30. A door is pushed on by two forces, a smaller (tilted) force at the door knob and a larger force nearer the hinge as shown. The door does not move. The force exerted on the door by the hinge....
1. is zero
2. points ­ (along +y)
3. points ¯ (along -y)
4. points (lower right, in diagram)
5. points in some other direction

31. A door is pushed on by two forces, a smaller (tilted) force at the door knob and a larger force nearer the hinge as shown. The door does not move. The force exerted on the door by the hinge....
1. is zero
2. points ­ (along +y)
3. points ¯ (along -y)
4. points (lower right, in diagram)
5. points in some other direction