Phys101 Term:122 Online HW-Ch12-Lec02
Ans:
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.
2Wcosθ
B.
Wsinθ
C.
2Tsinθ
D.
Tcosθ
E.
2Tcosθ
Tsinθ Tsinθ
|Mg�⃗| = W
Ans:
C ; Total vertical component of the pull of the strings is Tsin
θ + 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)
T
AC
0.3
Mg = 16 N
W = 96 N
T
BD
τ�⃗ net
= 0 ⇒ τ�⃗
TAC
+ τ�⃗
TBD
+ τ�⃗ w
+ τ�⃗ mg
= 0
Choose A to be axis of rotation ⇒ τ�⃗
TAC
= 0
−τ w
− τ
Mg
+ τ
TBD
= 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
×
10
8
N/m
2
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)
𝐀𝐧𝐬:
F�⃗
L
0
= 5 m ; V = 0.34 m; E = 125 × 10 8 N/m 2
∆L = ?
F
A = E
∆L
L
0
⇒ ∆L =
F
AE L 0
=
5000 × 5
0.363 × 125 × 10 8
= 5.51 × 10 −6 m
KFUPM-Physics Department 2