Answer:
Option (b) is correct.
Explanation:
The motion under the influence of gravity is called projectile motion.
The acceleration due to gravity is constant through out the motion and it is always acting downwards.
When an athlete jumps and follow the projectile path, it always have the same horizontal velocity as there is no acceleration in the horizontal direction.
Also he has the vertical acceleration constant which is equal to the acceleration due to gravity and acts towards the center of earth.
Option (b) is correct.
Explanation:
Given that,
The mean kinetic energy of the emitted electron, 
(a) The relation between the kinetic energy and the De Broglie wavelength is given by :
(b) According to Bragg's law,
n = 1
For nickel, 
As the angle made is very small, so such an electron is not useful in a Davisson-Germer type scattering experiment.
Answer: 154.08 m/s
Explanation:
Average acceleration 
is the variation of velocity 
over a specified period of time 
:
Where:
being 
the initial velocity and 
the final velocity
Then:
Since :
Finding :
Finally:
Velocity = 14 m/s
Time = 20 s
Displacement = Velocity×Time = (14×20) m = 280 m
The displacement is 280 m towards the direction of motion.
