Phys101
Term:122
Online HW-Ch12-Lec02
Q1:
A picture P of weight W is hung by two strings as shown. The magnitude of the
tension force of each string is T. The total vertical component of the pull of the
strings on the picture is:
A.
B.
C.
D.
E.
2Wcosθ
Wsinθ
2Tsinθ
Tcosθ
2Tcosθ
Tsinθ
Tsinθ
|Mg
�⃗| = W
Ans:
C ; Total vertical component of the pull of the strings is Tsinθ + Tsinθ = 2Tsinθ
Q2:
A uniform rod AB is 1.2 m long and weighs 16 N. It is suspended by strings AC and
BD as shown. A block P weighing 96 N is attached at E, 0.30 m from A. Find the
magnitude of the tension force (in N) of the string BD. (Give your answer in three
significant figures form)
TAC
TBD
0.3
Mg = 16 N
W = 96 N
Ans:
τ�⃗net = 0 ⇒ τ�⃗TAC + τ�⃗TBD + τ�⃗w + τ�⃗mg = 0
Choose A to be axis of rotation ⇒ τ�⃗TAC = 0
−τw − τMg + τTBD = 0 ⇒ − W(03) − Mg(0.6) + T(1.2)
⇒ T = �W(0.3)� + Mg((0.6) )/1.2 = 32.0
KFUPM-Physics Department
1
Phys101
Term:122
Online HW-Ch12-Lec02
Q3:
A 5.0 m long rod with a radius of 0.34 m and a Young's modulus of 125×108 N/m2 is
fixed horizontally at one end. A force of 5000 N is applied outwardly to the other end.
Find the elongation of the rod (in m). (Give your answer in three significant figures
form)
�⃗
F
𝐀𝐧𝐬:
L0 = 5 m ; V = 0.34 m; E = 125 × 108 N/m2
∆L = ?
F
∆L
=E
A
L0
⇒ ∆L =
F
5000 × 5
L0 =
= 5.51 × 10−6 m
8
AE
0.363 × 125 × 10
KFUPM-Physics Department
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