ABC is an equilateral triangle with O as its centre F1, F2 and F3 represent three forces acting on the sides AB, BC and AC respectively. If the total torque about O zero then the magnitude of F3 is
F1 +F2
F1 - F2
F1 +F2/2
F1 +F2/2
A.
F1 +F2
If we take clockwise torque
When a string is divided into three segments of length l1, l2, and l3 the fundamental frequencies of these three segments are v1, v2, and v3 respectively. The original fundamental frequency (v) of the string is
v = v1 +v2 +v3
C.
The fundamental frequency of string
The moment of inertia of a uniform circular disc is maximum about an axis perpendicular to the disc and passing through
B
C
D
D
A.
B
Moment of inertia of circular disc = 1/2mR2
Thus, as the distance between the centre and the point increases, a moment of inertia increases.
Two persons of masses 55 kg and 65 kg respectively. are at the opposite ends of the boat. The length of the boat is 3.0 m and weigh 100 kg. The 55 kg man walks to the 65 kg man and sits with him. If the boat is in still water the centre of mass of the system shifts by
3.0 m
2.3 m
zero
zero
C.
zero
Here on the entire system net external force on the system is zero hence centre of mass remains unchanged.
When a mass is rotating in a plane about a fixed point, its angular momentum is directed along
a line perpendicular to the plane of rotation
the line making an angle of 45o to the plane of rotation
the radius
the radius
A.
a line perpendicular to the plane of rotation
We knows L = m (r x v)
So, here, angular momentum is directed along a line perpendicular to the plane of rotation.