Answer: i think c
Explanation:QA: “What is ordinary glass made of ?”
Glass is mostly silica, or silicon dioxide, present as quartz in many types of sand. Pure silica forms a highly transparent glass, but has a very high melting or softening temperature, around 1700°C. Even at such high temperatures it is highly viscous and difficult to work. Its use is largely confined to applications requiring high transparency to ultra-violet and infra-red radiation, stability at elevated temperatures or low thermal expansion coefficient.
“Ordinary glass” windows and drinking vessels are typically made from soda-lime glass, containing silica with around 25% sodium, calcium and other oxides, which together reduce the softening temperature to roughly 500–600°C
A coil of insulated wire around an iron core
Answer:
Explanation:
let 
be the mass attached, let 
be the spring constant and let 
be the positive damping constant.
-By Newton's second law:
where 
is the displacement from equilibrium position. The equation can be transformed into:
shich is the equation of motion.
Answer:
1 inch = 2.54 cm
12.9 inches= 12.9 x 2.54
= 32.766
= 32.8 cm (approximately)
Hope it helps...
