Answer:
The force exerted by three charges on the fourth is 
Explanation:
Given:
- The magnitude of three identical charges,

- Length of the edge of the square a=3 cm
- Magnitude of fourth charge ,Q=3 nC
According to coulombs Law the force F between any two charge particles is given by

where r is the radial distance between them.
Since the force acting on the charge particle will be in different directions so according to triangle law of vector addition

The gravitational pull is weaker.
Answer:
0.76 s
Explanation:
We are given that
Length of rod,L=20 cm=
1 m=100 cm
Mass of rod,M=190 g=
Mass of ball,m=19 g=
Using 1 kg=1000g
We have to find the period if the rod and clay swing as a pendulum.
Moment of inertia of rod-clay=Moment of inertia of rod+moment of inertia of clay


Substitute the values then we get


Now, the center of mass of the combination of the rod and clay is given by

Substitute
=Distance between pivot and the center of the rod
The distance between rod and clay
Using the formula

m
Time period of the oscillation of the system of the rod and the clay is given by

g=
Using the formula
Time period=
Time-period=0.76 s
Hence, the period =0.76 s