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Province of the
EASTERN CAPE
EDUCATION
DIRECTORATE SENIOR CURRICULUM MANAGEMENT (SEN-FET)
HOME SCHOOLING SELF-STUDY WORKSHEET ANSWER SHEET
SUBJECT
WELDING & METALWORK
GRADE
DATE
APRIL 2020 WK 3
TOPIC
FORCES: MEMORANDUM
TERM 1
REVISION
(Please tick)
TERM 2 CONTENT
(√)
QUESTION 1
QUESTION 2
A diagram below shows a uniform beam. The beam is supported at points RL and RR. Three point loads of 4 N, 5 N and 3 N are exerted onto the beam.
a) Calculate the reactions at supports RL and RR.
b) Calculate the bending moments at point B, C and D.
c) Draw a bending-moment diagram of the beam.
Solution a)
Reactions at the supports RL and RR:
RL x 12 = (3 x 3) + (5 x 6) + (4 x 9)
: RL = 6.25N
RR x 12 = (4 x 3) + (5 x 6) + (3 x 9)
RR = 5.75N
Solution b)
Bending moments:
BMB = (6.25 N x 3 m)
= (18.75 N.m)
BMc = (6.25 x 6) – (4 x 3)
= 25.5 N.m
BMD = (6.25 x 9) – (4 x 6) – (5 x 3)
= 17.25 N.m
Solution c)
Question 3
Solution a)
Reactions at the supports RL and RR
Moments about RR
RL x 12 = (5 x 9) + (6 x 6) + (4 x 3)
RL x 12 = 45 + 36 + 12
RL =
RL = 7,75 N
Reactions about RL
RR x 12 = (4 x 9) + (6 x 6) + (5 x 3)
RR x 12 = 36 + 36 + 15
RR =
RR = 7,25 kN
Solution b)
Shear forces:
𝑆𝐹𝐴 = 0 kN.
𝑆𝐹𝐵 = 7,75 – 5
= 2,75 kN
𝑆𝐹𝐶 = 7,75 – 5 – 6
= - 3, 25 kN
𝑆𝐹𝐷 = 7,75 – 5 – 6 – 4
= - 7,25 kN
𝑆𝐹𝐸 = 7,75 – 5 – 6 – 4 + 7,75
= 0 kN
Solution c)
Bending moments:
Solution d)
Shear force diagram:
Solution e)
Bending moment diagram:
QUESTION 4