Answer:
The correct option is a
Explanation:
This question seeks to test a general rule in physics (on charges) which states that <u>like charges repel but unlike charges attract</u>. This means that, a negatively charged substance will repel or not attract another negatively charged material and the same applies to a positively charged substance also. However, a <u>negatively charged substance will attract a positively charged material and vice versa,</u> hence only a negatively charged rod will attract a positively charged hanging ball.
Answer:
Explanation:
reading of scale = reaction force of surface R
centripetal force = R - mg = m v² / R , m is mass , v is velocity and R is radius of the circular path .
R = mg + m v² / R
given ,
m v² / R = .80 mg
v² = .80 x g x R
= .8 x 9.8 x 9 = 70.56
v = 8.4 m /s
Centripetal acceleration is given by the formula

Since we know the value of the acceleration is 9.8 m/s² and we know r, we can solve for the speed, which is the magnitude of v. Note the value of a is just the acceleration due to gravity, which is what makes the rocket orbit and not fly off into space.