The binding energies of K-shell and L-shell electrons in a certain metal are EK and EL, respectively, If a Kαx ray from this met
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Answer:
The correct answer is option 'c': 30 AUs
Explanation:
For a spherical wave front emitted by sun with total energy 'E' the energy density over the surface when it is at a distance 'r' from the sun is given by
This energy per unit area is sensed by observer as intensity of the sun.
Let the initial intensity of sun at a distance be
Thus if the sun becomes 900 times dimmer we have
Thus the distance increases 30 times.
The height of the building is 53.4 m (projectile motion)
Explanation:
The motion of the ball is a projectile motion, so it follows a parabolic path which consists of two independent motions:
- A uniform motion (constant velocity) along the horizontal direction
- An accelerated motion with constant acceleration (acceleration of gravity) in the vertical direction
First of all, we consider the horizontal motion, which is a uniform motion at constant speed. The equation that gives the horizontal distance travelled is:
where:
is the horizontal velocity of the ball, which is constant since there are no forces in this direction
d = 165 m is the horizontal distance travelled by the ball
Solving for t, we find the time of flight:
Now we analyze the vertical motion: it is an accelerated motion, we can use the suvat equation
where
s is the vertical displacement, which is the height of the building
u = 0 is the initial vertical velocity of the ball
t = 3.3 s is the time of flight
is the acceleration of gravity
Solving for s, we find the height of the building:
Learn more about projectile motion here:
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