X-rays with high photon energies (above 5–10keV, below 0.2–0.1nm wavelength) are called hard X-rays, while those with lower energy (and longer wavelength) are called soft X-rays. Due to their penetrating ability, hard X-rays are widely used to image the inside of objects, e.g., in medical radiography and airport security. By contrast, soft X-rays are easily absorbed in air; the attenuation length of 600 eV (~2nm) X-rays in water is less than 1 micrometer.
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When you climb, earth exerts gravitational force on pack in downward direction(pointing towards the center of earth).
In order to climb, you need to work against work done by gravity on the pack.
Hence work done by you = work done by gravity on pack
= Force x displacement = 70 x 30 = 2100 J.
So you need to do 2100 joules of work to lift your pack.
Power is the rate of work done.
Therefore power = work done by you/time(in seconds)
= 2100/600 =3.5 watts
The net force on the cart is 100 N in the direction of its motion, so by Newton's second law we can find the acceleration <em>a</em> applied to it:
100 N = (50 kg) <em>a</em>
<em>a</em> = (100 N) / (50 kg)
<em>a</em> = 2 m/s²
The cart starts at rest and travels a distance of 10 m, so that its final velocity <em>v</em> satisfies
<em>v</em> ² - 0² = 2 (2 m/s²) (10 m)
<em>v</em> ²= 40 m²/s²
and so the cart ends up with kinetic energy
KE = 1/2 <em>m</em> <em>v</em> ² = 1/2 (50 kg) (40 m²/s²) = 1000 J
A roller coaster car starts from the rest from a first summit, descends a vertical distance of 45 meters and then climbs a second summit, reaching the top with a speed of 15m / s. How high is the second summit? Do not consider friction
