# Strength of Materials Questions and Answers – Center of Gravity

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Center of Gravity”.

1. The point through which the whole weight of the body acts is called _____________
a) Inertial point
b) Center of gravity
c) Centroid
d) Central point

Explanation: The centre of gravity of a body is the point through which the whole weight of the body acts. A body’s center of gravity is the point around which the resultant torque due to gravity forces vanishes. Where a gravity field can be considered to be uniform and the centre of gravity will be the same.

2. The point at which the total area of a plane figure is asssumed to be concentrated is called ____________
a) Centroid
b) Centre of gravity
c) Central point
d) Inertial point

Explanation: The centroid is the point at which the total area of a plane figure is assumed to be concentrated. The centroid and centre of gravity are at the same point.

3. Where will be the centre of gravity of a uniform rod lies?
a) At its end
b) At its middle point
c) At its centre of its cross sectional area
d) Depends upon its material

Explanation: The centre of gravity of a uniform rod lies at its middle point. The whole weight of the rod acts through its middle point.

4. Where the center of gravity of a circle lies?
a) At its centre
c) Anywhere on its circumference
d) Anywhere on its diameter

Explanation: The whole weight of a circle can be assumed to act through its center. So the center of gravity of a circle is at its center.

5. Where will be the center of gravity of the following section will lie In coordinates?

a) (6,3)
b) (6,6)
c) (6,1.5)
d) (1.5,3)

Explanation: The centre of gravity of this rectangular area will be half of 3cm from x-axis and half of 12 from the y-axis. therefore the center of gravity will be at (6,1.5).
Note: Join free Sanfoundry classes at Telegram or Youtube

6. Where will be the centre of gravity of the T section shown in the figure?

a) At 8.545cm
b) At 6.5cm
c) At 5cm
d) At 9.25cm

Explanation: The center of gravity is given by, y = (a1y1 + a2y2) / (a1 + a2) = ( 36×11.5 + 30×5) / (36+30) = 8.545cm.

7. Where will be the center of gravity of the L-section shown in the figure?

a) (1.28,2.64)
b) (1.45,3.24)
c) (1.64,3.28)
d) (2.24,3.68)

Explanation: The center of gravity is given by, y = (a1y1 + a2y2) / (a1 + a2) = (10×3.5 + 4×0.5) / (10+4) = 2.64cm.
This will on for the y-axis.
For the x-axis, The center of gravity is given by, x = (a1x1 + a2x2) / (a1 + a2) = (0x1 + 4×2) / (10+4) = 1.28cm.
So the center of gravity will be at (2.33, 4.33).

8. Where will be the center of gravity of the figure shown ?

a) (3.45,4.52)
b) (3.59,7.42)
c) (3.66,8.84)
d) (3.88,8.88)

Explanation: Area of triangle = 50, area of rectangle = 100
The center of gravity is given by, y = (a1y1 + a2y2) / (a1 + a2) = (50×20/3 + 100×10) / (50+100) = 8.88cm.
This will on for the y-axis.
For the x-axis, The center of gravity is given by, x = (a1x1 + a2x2) / (a1 + a2) = (50×6.66 + 100×2.5) / (50+100) = 3.88cm.
So the center of gravity will be at (2.33, 4.33).

9. Where will be the center of gravity of an I section will be if the dimension of upper web is 2x10cm, lower web is 2×20 and that of flange is 2x15cm If the y-axis will pass through the center of the section?
a) 7.611cm
b) 9.51cm
c) 9.31cm
d) 11.5cm

Explanation: The center of gravity is given by, y = (a1y1 + a2y2 + a3y3) / (a1 + a2 + a3) = (20×18 + 30×9.5 + 40×1 / (20 +30+40) = 1.611cm.