Ascientist is giving a demonstration with a van de graaff generator in a class about electrostatics. the scientist can detect the type of charge on the van de graaff generator by
a) bringing a positively charged balloon near it.
b) seeing if it picks up bits of paper from a surface.
c) touching it with a metallic rod that conducts charge.
d) testing if it attracts a neutral sphere made of plastic.

A) bringing a positively charged balloon near it.

Explanation:

This is the correct answer because is the only option in which the object has a charge (a positive one in this case). That means when the scientist brings a positively charged balloon near the hollow metal globe on the top of the Van de Graaff generator a repulsion is seen it because the globe is positively charged too.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s