Answer:

Explanation:
Average velocity of oxygen molecule at given temperature is

now we have
M = 32 g/mol = 0.032 kg/mol
T = 27 degree C = 300 K
now we have


now for de Broglie wavelength we know that



Hope this helps. If you need clarification just ask me!
Answer:
The final velocity of the cart is
Explanation:
From the question we are told that
The mass of the girl is 
The mass of the cart is 
The speed of the cart and kid(girl) is 
The final velocity of the girl is 
Let assume that velocity eastward is positive and velocity westward is negative (Note that if we assume vise versa it wouldn't affect the answer )
The total momentum of the system before she steps off the back of the cart
is mathematically evaluated as

substituting values


The total momentum after she steps off the back of the cart is mathematically evaluated as

Where
is the final velocity of the cart
substituting values


Now according to the law of conservation of momentum

So

=> 
Since the value is positive it implies that the cart moved eastward
Answer:
The second kinetic energy is 162 J.
Explanation:
Given that,
Mass, 
Velocity, 
Kinetic energy, 
Mass, 
Velocity, 
We need to find kinetic energy
. Kinetic energy is given by :

So,

So, the second kinetic energy is 162 J.