Answer:hot air
Explanation:Hot air goes up, so when you put it in a hot air balloon fire is placed at the oppening to creat hot air and lift the balloon! :)
1.Velocity (v) is a vector quantity that measures displacement (or change in position, Δs) over the change in time (Δt), represented by the equation v = Δs/Δt. Speed (or rate, r) is a scalar quantity that measures the distance traveled (d) over the change in time (Δt), represented by the equation r = d/Δt.
Answer:
Focal length is 12 cm
Nature is Convex lens
Explanation:
Object distance=p= 10 cm
Image distance =q = -60 cm (Image is at the same side)
focal length= f = ?
According to lens equation
1/f = 1/p + 1/q
1/f = 1/10 + 1/(-60)
1/f = 1/10 - 1/60
1/f = 5/60
or
f= 12 cm
(It is a convex lens because focal length is positive)
Answer:

Explanation:
Refraction: It is a process in which light ray travel from one medium to another medium.
When a light travel form one medium to another medium then the speed of light changes.
When a light travel from rare to denser medium then the light bend towards normal .
When a light travel form denser to rare medium then the light ray bend away from the normal.
Refractive index:It is a ratio of velocity of light in vacuum to the velocity of light in medium .It is a measure of change in speed of light when it passes from vacuum into material.It is represented by "n''.
Mathematical representation:

Where n=Refractive index of material
c=Velocity of light in vacuum
v=Velocity of light in medium
<h3> it depends on numbers of turns coils area restoring force per unit twist and magnetic fields</h3><h2 /><h2 /><h2>hope it helps</h2>