A twig from a tree drops from a 200m high cliff on to a beach below.during its fall 40% twig's energy is converted into thermal
1 answer:
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a) The kinetic energy (KE) of an object is expressed as the product of half of the mass (m) of the object and the square of its velocity (v²):
It is given:
v = 8.5 m/s
m = 91 kg
So:
b) We can calculate height by using the formula for potential energy (PE):
PE = m*g*h
In this case, h is eight, and PE is the same as KE:
PE = KE = 3,287.4 J
m = 91 kg
g = 9.81 m/s² - gravitational acceleration
h = ? - height
Now, let's replace those:
3,287.4= 91 * 9.81 * h
⇒ h = 3,287.4/(91*9.81) = 3,287.4/892.7 = 3.7 m
Answer:
They have a dual wave-particle nature.
Explanation:
Electromagnetic waves consist of periodic oscillations of electric and magnetic field in a plane perpendicular to the direction of motion of the wave (in fact, they are also classified as transverse waves).
Electromagnetic waves have a wave nature, however they also have particle nature - in fact, it has been proved in some experiment (e.g. photoelectric effect) that in some conditions they act as packets of particles - called photons. Therefore, the option
They have a dual wave-particle nature.
is correct.
Other options are wrong because:
They are all invisible. --> False because visible light (which is part of the electromagnetic spectrum, so they are electromagnetic waves) is visible
They can only travel without a medium. --> False because they can also travel in a vacuum
They are slower than sound waves. --> False because they travel much faster (they travel at the speed of light in a vacuum, , while sound travels at 343 m/s in air, for instance)
Answer:
<u>6 bulbs</u> are needed to illuminate the room.
Explanation:
Given:
Measurement of kitchen (A) = 10 ft by 10 ft = 100 sq. ft
Number of footcandles (n) = 50
Lumens emitted by 1 bulb = 834
Number of bulbs (N) = ?
We are also given,
1 foot candle = 1 lumen/sq. ft
So, 50 foot candles = 50 lumens/sq. ft
Now, for an area of 1 sq. ft 50 lumens are emitted.
So, for an area of 100 sq. ft, lumens emitted = 50 × 100 = 5000 lumens
Now, one bulb emits = 834 lumes
Therefore, number of bulbs required for emitting 5000 lumens is given as:
So, 6 bulbs are needed to illuminate the room.