Answer:

where E = electric field intensity
Explanation:
As we know that plastic ball is suspended by a string which makes 30 degree angle with the vertical
So here force due to electrostatic force on the charged ball is in horizontal direction along the direction of electric field
while weight of the ball is vertically downwards
so here we have


since string makes 30 degree angle with the vertical so we will have





where E = electric field intensity
Answer:
Option B, Fix the piston in place so the volume of the pas remains constant
Explanation:
As we know

The effect on variable due to another variable can be studied by keeping the third variable constant.
Hence, in order the study the variation of temperature with pressure or vice versa, the volume needs to fixed at a certain value.
Hence, option B is correct
Answer:
option E
Explanation:
given,
diameter = 4 mm
shutter speed = 1/1000 s
diameter of aperture = ?
shutter speed = 1/250 s
exposure time to the shutter time

N is the diameter of the aperture and t is the time of exposure
now,


inserting all the values

N₂² = 4
N₂ = 2 mm
hence , the correct answer is option E
Answer:
Velocity
Explanation:
Objects in motion usually have a speed which is scalar or velocity which is a vector.
A scalar quantity is one with magnitude but has no directional attribute.
A vector quantity is one with both magnitude and directional attribute.
Speed is a scalar quantity that describes the magnitude of motion a body accrues.
Velocity is a vector quantity that describes both the magnitude of motion and the direction of motion in a body.