Answer:
This process is known as static electricity
Explanation:
When balloon is rubbed on the wool , a negative charge is usually formed. When the balloon is then held over—but not touching—some bits of paper, some of the bits jump up to the balloon. The bits which jump up to the balloon are positive charged and we know that unlike charges attract.
This process explains static electricity which is when the charges on a material are not in a balanced state.
Answer:

Explanation:
consider the mass of each train car be m
m₁ = m₂ = m₃ = m
speed of the three identical train
u₁ = u₂ = u₃ = 1.8 m/s
m₄ = m u₄ = 4.5 m/s
m₅ = m u₅ = 0 (initial velocity )
final velocity
v₁ = v₂ = v₃ = v₄ = v₅ = v
using conservation of momentum
m₁u₁ + m₂u₂ + m₃u₃ + m₄u₄ + m₅u₅ = m₁v₁ + m₂v₂ + m₃v₃ + m₄v₄ + m₅v₅
m (1.8 + 1.8 + 1.8 +4.5) = 5 m v


Answer:
The momentum before is equal to the momentum after
Explanation:
It is equal and should level out in an equation.
Answer:
The possible thickness of the soap bubble = 
Explanation:
<u>Given:</u>
- Refractive index of the soap bubble,

- Wavelength of the light taken,

Let the thickness of the soap bubble be
.
It is given that the soap bubble appears very bright, it means, there is a constructive interference takes place.
For the constructive interference of light through a thin film ( soap bubble), the condition of constructive interference is given as:

where
is the order of constructive interference.
Since the soap bubble is appearing very bright, the order should be 0, as
order interference has maximum intensity.
Thus,

It is the possible thickness of the soap bubble.