Questions 1 A stone falls from rest from the top of a high tower. Ignore
air resistance and take g = 10 m/s2
a What is its velocity after
() 15
(ii) 25,
(iii) 35,
(iv) 5s?
b How far has it fallen after
(i) 15,
(ii) 2s,
(iii) 35,
(iv) 5s?
2 An object falls from a hovering helicopter and hits the
ground at a speed of 30 m/s. How long does it take the
object to reach the ground and how far does it fall? Sketch
a velocity-time graph for the object (ignore air resistance).

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.