Answer:
Tension, T = 0.0115 N
Explanation:
Given that,
Mass of the plastic ball, m = 1.1 g
Length of the string, l = 56 cm
A charged rod brought near the ball exerts a horizontal electrical force F on it, causing the ball to swing out to a 21.0 degree angle and remain there. According to attached figure :

T is tension in the string

So, the tension in the string is 0.0115 N.
Answer: True
Explanation:
Pencils indeed should not be used as tools when working inside a computer because it is made of Lead.
Lead is a conductor of electricity and as such if it is left inside the computer at even miniscule quantities, it can redirect electricity and damage components in the process.
If one wants to work inside a computer, it is best to use tools like tweezers and needle-nose pliers.
Answer:
Incorrect statement is (b).
Explanation:
Option (a) : There is an inverse relation between the time and the frequency. The time taken depends on the frequency of the number of oscillations. Statement 1 is correct i.e. the time taken by any point of the wave to make one complete oscillation does not depend on the amplitude.
Option (b) : Speed of a wave is given by the product of its frequency and wavelength. It is not necessary that doubling the wavelength of the wave will halve its frequency as speed depends on the medium.
Option (c) : Doubling the amplitude has no effect on on the wavelength as amplitude does not depends on its wavelength.
Option (d) : Since, 
Speed is directly proportional to the frequency and wavelength. So, doubling the frequency of the wave will double its speed. So, the incorrect statement is (b).
Answer:
33.65°
Explanation:
radius, r = 53.1 m
m = 2.9 Mg = 2.9 x 10^6 g = 2900 kg
v = 67 km/h
convert km/h into m/s
v = 18.61 m/s
Let the angle of banking of road is θ, without friction


tan θ = 0.6655
θ = 33.65°
Thus, the angle of banking of road is 33.65°.