Answer:
0.7515875 eV

Explanation:
f = Maximum frequency = 
h = Planck's constant = 
W = Work function = 2.52 eV
Converting to Joules

Maximum photon energy is given by

Maximum Kinetic energy is given by

Converting to eV

The maximum kinetic energy of electrons ejected from this surface is 0.7515875 eV

The range of frequencies for which no electrons are ejected is

The horizontal is s or displacement
The vertical is t or time
The first question's answer is :
If, F=ma
Then, 15N= 2.1kg (a)
15/2.1=a
7.14=a
Therefore, acceleration = 7.14m/s^2
sorry I am not sure about the second question :-(
Answer:
Part a)
the tension force is equal to the weight of the crate
Part b)
tension force is more than the weight of the crate while accelerating upwards
tension force is less than the weight of crate if it is accelerating downwards
Explanation:
Part a)
When large crate is suspended at rest or moving with uniform speed then it is given as

here since speed is constant or it is at rest
so we will have


so the tension force is equal to the weight of the crate
Part b)
Now let say the crate is accelerating upwards
now we can say


so tension force is more than the weight of the crate
Now if the crate is accelerating downwards


so tension force is less than the weight of crate if it is accelerating downwards
Answer:cross-sectional area, and thus surface area, increases the amount of air resistance an object experiences
Explanation: