1. The connecting rod of an engine mechanism has an angular acceleration of 1200 rad/s^2. Using velocity and acceleration diagrams, the acceleration of the connecting rod's center of gravity G is found to be 414 m/s^2, and the angular acceleration of connecting rod AB is 546 rad/s^2. 2. A four-bar linkage is shown with given link lengths and a rotating crank. With the crank at an angle of 60 degrees, velocity and acceleration diagrams are drawn to determine the angular velocity and acceleration of links QR and RS.

1. Acceleration analysis

2. Problem 1
• An engine mechanism is shown in figure. The crank CB = 100 mm and the
connecting rod BA = 300 mm with centre of gravity G, 100 mm from B. In
the position shown, the crankshaft has a speed of 75 rad/s and an angular
acceleration of α = 1200 rad/s2.
• Find: 1. Acceleration of G
2. angular acceleration of AB.

3. Find velocity of Crank BC
• ω = 75 rad/s
• v BC = ω x BC = 75 x 0.1 = 7.5 m/s

4. Draw Velocity Diagram
• Scale for velocity diagram : 1m/s = 1cm
1. vAB = vector ab = 4 m/s
2. vA = vector ca
3. vG = vector cg = 6.8 m/s

5. Find velocity of all Links and radial
acceleration
Link Velocity, v m/s
BC (Crank) 7.5 526.5 1200*0.1 = 120
AB (Connecting Rod) 4 53.3 Find from
acceleration diagram

6. Step 1 List out fixed point
c’

7. Step 2 Draw Radial acceleration of Crank BC
towards point C (center)
c’
b’’

8. Step 3 Draw Tangential acceleration of Crank BC
perpendicular to Radial acc.
c’
b’’
b’

9. Step 4 Draw Radial acceleration of connecting
rod AB directio towards point B
c’
b’’
b’
x

10. Step 5 Draw Tangential acceleration of AB
perpendicular to Radial acc. Of AB
c’
b’’
b’
x

11. Step 6 Draw acceleration line for slider A in
direction of motion of slider
c’
b’’
b’
x
a’

12. Step 6 Find G point on vector b’a’ and join cg’
• Vector c’g’ is acceleration of
point G
• aG = vector c' g' = 414 m/s2
• at for AB = vector xa’ = 546
m/s2
c’
b’’
b’
x
a’
g’

13. Problem 2
• PQRS is a four bar chain with link PS fixed. The lengths of the
links are PQ = 62.5 mm ; QR = 175 mm ; RS = 112.5 mm ; and
PS = 200 mm. The crank PQ rotates at 10 rad/s clockwise.
Draw the velocity and acceleration diagram when angle QPS =
60° and Q and R lie on the same side of PS. Find the angular
velocity and angular acceleration of links QR and RS.