Answer:
2.9 E14 Hz
Explanation:
As we know by Einstein's equation that energy incident on the photo sensitive surface will be used by the surface to eject electron out of the surface with some kinetic energy.
This is given by

now the threshold frequency is the minimum frequency of the incident photons due to which electrons are ejected out with minimum kinetic energy or least kinetic energy.
So here when KE = 0 in the graph then corresponding to that position the frequency will be given as threshold frequency
so here from graph when KE = 0

Explanation:
It is given that,
Speed of the ball, v = 10 m/s
Initial position of ball above ground, h = 20 m
(a) Let H is the maximum height reached by the ball. It can be calculated using the conservation of energy as :


h' = 5.1 m
The maximum height above ground,
H = 5.1 + 20
H = 25.1 meters
So, the maximum height reached by the ball is 25.1 meters.
(b) The ball's speed as it passes the window on its way down is same as the initial speed i.e. 10 m/s.
Hence, this is the required solution.
Answer:
diagram: see image, x-component: 84.3 N, acceleration: 4.38 m/s^2
Explanation:
(see image for further explanation)
plane is flying at an altitude of 70 m
now if an object is dropped from it then time taken by object to drop on ground will be given as

here initial speed in vertical direction must be zero as plane is moving horizontal
given that
y = 70 m
a = 9.8 m/s^2


now since the plane is moving horizontally with speed v = 44 m/s
so the horizontal distance moved by the object will be



so the distance moved by the box is 166.3 m
Answer:
average speed is 60km/h
Explanation:
you sum up the speed attained in each distance covered and divide it by 2 to get your answer