The mass number of an element tells us the number of protons AND neutrons in an atom (the two particles that have a measurable mass). Sodium has a mass number of 23amu. Since sodium has 11 protons, the number of neutrons must be 23 – 11 = 12 neutrons.
 
        
             
        
        
        
Answer:
The force parallel to the horizontal is 26.24 N
Explanation:
She pulls on the leash with a force F = 30 N, this force, since its at an angle of 29° (i will cal this angle  ), it has a force component on x (the horizontal, i will call this force
), it has a force component on x (the horizontal, i will call this force  ) and a force component on y (the vertical, i will call this
) and a force component on y (the vertical, i will call this  ).
 ).
This can be seen in the attached picture.
Since we are asked about the force parallel to the horizontal, we need to find the component of the force  , since
, since  is the adjacent angle, we need to use cosine:
 is the adjacent angle, we need to use cosine:

since  and
 and 



The force parallel to the horizontal is 26.24 N
 
        
             
        
        
        
Answer:
a) They are in the same point
b) t = 0 s, t = 2.27 s, t = 5.73 s
c) t = 1 s, t = 4.33 s
d) t = 2.67 s
Explanation:
Given equations are:


Constants are:

a) "Just after leaving the starting point" means that t = 0. So, if we look the equations, both  and
 and  depend on t and don't have constant terms.
 depend on t and don't have constant terms.
So both cars A and B are in the same point.
b) Firstly, they are in the same point in x = 0 at t = 0. But for generalized case, we must equalize equations and solve quadratic equation where roots will give us proper t value(s).


 s,
 s,  s
 s
c) Since the distance isn't changing, the velocities are equal. To find velocities, we need to take the derivatives of both equations with respect to time and equalize them.

 s,
 s,  s
 s
d) For same acceleration, we we need to take the derivatives of velocity equations with respect to time and equalize them.
 s
 s