Given:
distance from the projector lens to the image, di
projector lens focal length, f
distance from the transparency to the projector lens, do
thin lens equation: 1/f = 1/di + 1/do
do = 4 inches
di = 8 feet
convert feet to inches, for uniformity.
1 foot = 12 inches
8 feet * 12 inches/ft = 96 inches
1/f = 1/96 inches + 1/4 inches
Adding fractions, denominator must be the same.
1/f = (1/96 * 1/1) + (1/4 * 24/24)
1/f = 1/96 + 24/96
1/f = 25/96
to find the value of f, do cross multiplication
1*96 = f * 25
96 = 25f
96/25 = f
3.84 = f
The focal length of the project lens is 3.84 inches
The answer is a
Hope this helps!
Answer:
Tension, T = 87.63 N
Explanation:
Given that,
Mass of the object, m = 6.9 kg
The string is acting in the upward direction, a = 2.9 m/s²
Acceleration due to gravity, g = 9.8 m/s²
As the lift is accelerating upwards, it means the net force acting on it is given by :
T = m(a+g)
= 6.9 (2.9+9.8)
= 6.9(2.7)
= 87.63 N
So, the tension in the string is 87.63 N.
It creates a white crystal salt MgF2
