Solved GATE Questions on Gear Trains
Question 1. The sun gear in the figure is driven clockwise at 100 rpm. The ring gear is held stationary. For the number of teeth shown on the gears, the arm rotates at
(A) 0 rpm
(B) 20 rpm
(C) 33.33 rpm
(D) 66.67 rpm
GATE-ME-2001
Hint 1. (Ans B)
|
Arm |
Sun |
Planet |
Ring |
|
+1 |
+1 |
+1 |
+1 |
|
0 |
 |
-80/30 |
-1 |
|
1 |
5 |
-5/3 |
0 |
Question 2. The minimum number of teeth on the pinion to operate without interference in standard full height involute teeth gear mechanism with 20°pressure angle is
(A) 14
(B) 12
(C) 18
(D) 32
GATE-ME-2002
Hint 2. (Ans C)
Data for Question 3 and 4 is given below. Solve the problem and choose the correct answers.
A compacting machine shown in the figure below is used to create a desired thrust force by using a rack and pinion arrangement. The input gear is mounted on the motor shaft. The gear have involute teeth of 2mm module.
Question 3. If the drive efficiency is 80%, then torque required on the input shaft to create 1000 N output thrust is
(A) 20 Nm
(B) 25 Nm
(C) 32 Nm
(D) 50 Nm
GATE-ME-2004
Hint 3. (Ans B)
Given : Module m=2
OR
Let 
be he torque applied by the motor
be the torque applied by gear.
power transmission =80%
Now, 
Question 4. If the pressure angle of the rack is 20
, then force acting along the line of action between the rack and gear teeth is
(A) 250 N
(B) 342 N
(C) 532 N
(D) 600 N
GATE-ME-2004
Hint 4. (Ans C)
Question 5. In a cam-follower mechanism, the follower needs to rise through 20 mm during 60
of cam rotation, the first 30
with a constant acceleration and then with a deceleration of the same magnitude. The initial and the final speeds of the follower are zero. The cam rotates at a uniform speed of 300 rpm. The maximum speed of the follower is
(A) 0.60 m/s
(B) 1.20 m/s
(C) 1.68 m/s
(D) 2.40 m/s
GATE-ME-2005
Hint 5. (Ans B)
Angular velocity
Time taken to move 30
During this time, follower moves by distance 20 mm with initial velocity
Common Data for Question 6 and 7:
A planetary gear train has four gears and one carrier. Angular velocities of the gears are 
respectively. The carrier rotates with angularvelocity 
.
Question 6. What is the relation between the angular velocities of Gear 1 and Gear 4?
(A) 
(B) 
(C) 
(D) 
GATE-ME-2006
Hint 6. (Ans A)
As, 
Question 7. For 
rpm clockwise (cw) when looked from the left, what is the angular velocity of the carrier and its direction so that Gear 4 rotates in counter clockwise (ccw) direction at twice the angular velocity of Gear 1 when looked fropm the left?
(A) 130 rpm, cw
(B) 223 rpm, ccw
(C) 256 rpm, cw
(D) 156 rpm, ccw
GATE-ME-2006
Hint 7. (Ans D)
Question 8. Match the items in columns I and II.
| Column I | Column II |
| (P) Addendum | (1) Cam |
| (Q) Instantaneous centre of velocity | (2) Beam |
| (R) Section modulus | (3) Linkage |
| (S) Prime circle | (4) Gear |
(A) P-4, Q-2, R-3, S-1
(B) P-4, Q-3, R-2, S-1
(C) P-3, Q-2, R-1, S-4
(D) P-3, Q-4, R-1, S-2
GATE-ME-2006
Hint 8. (Ans B)
Answer keys
1. (B) 2. (C) 3. (B) 4. (C) 5. (B) 6. (A) 7. (D) 8. (B)