Answer:
f = 5 cm
Explanation:
using the thin lens equation, given as follows:

where,
f = focal length = ?
do = the distance of object from lens = 20 cm
di = the distance of image from lens = 6.6667 cm
Therefore,

<u>f = 5 cm</u>
Always true everthing has gravity
Answer:
a) 75.5 degree relative to the North in north-west direction
b) 309.84 km/h
Explanation:
a)If the pilot wants to fly due west while there's wind of 80km/h due south. The north-component of the airplane velocity relative to the air must be equal to the wind speed to the south, 80km/h in order to counter balance it
So the pilot should head to the West-North direction at an angle of

relative to the North-bound.
b) As the North component of the airplane velocity cancel out the wind south-bound speed. The speed of the plane over the ground would be the West component of the airplane velocity, which is

Answer:
0.04
Explanation:
Fraction of power converted to sound = 80% = 0.08
Fraction incident upon each eardrum onstage = 0.08/2 = 0.04