Answer:
1 / f = 1 / o + 1 / i = (i + o) / o * 1
f = o * i / (o + i) = 60 * 30 / (60 + 30) = 1800 / 90 = 20 cm
Both the object and image are in positive space for a mirror
Answer:
The material stretched across the drum vibrates to produce the sound waves.
Explanation:
A drum is one of the oldest musical instrument made by man. It is made of a hollow body over which a material such as skin is stretched. When a drum is struck with a stick, the material vibrates up and down. This makes the air above the drum to contract and relax rhythmically resulting in soundwaves. The soundwaves travel through air to reach our ears where they are heard.
The quality of sound produced by a drum is affected by its shape. A larger drum produces a lower pitched sound.
Answer:
18.24 seconds
Explanation:
First you convert the km/h to m/s, 70km/h=(175/9)m/s,85km/h=(425/18)m/s.
You know it took 10 seconds for the police to reach 85 km/h. Calculate the distance that the car is ahead of the police (175/9)*10=1750/9m. Then by divide 1750/9 with 425/18, you will get the value 8.24. Add the 10 seconds with the 8.24 you will get 18.24 sec which is the total time.