Answer:
The answer of the part (a) is v2 = 7.09 m/s
and the answer of the part (b) is vA1 = 5.25 m/s
Explanation:
Explanation of the both parts of answer is in the following attachments
Answer:

Explanation:
It is given that,
Initially, the electron is in n = 7 energy level. When it relaxes to a lower energy level, emitting light of 397 nm. We need to find the value of n for the level to which the electron relaxed. It can be calculate using the formula as :


R = Rydberg constant, 

Solving above equation we get the value of final n is,

or

So, it will relax in the n = 2. Hence, this is the required solution.
Answer:
Explanation:
Expression for time period of pendulum is given as follows

where l is length of pendulum and g is acceleration due to gravity .
Putting the given values for first place

Putting the values for second place

Dividing these two equation

T = 2.66455 s.
Answer:
This depends on what angle they are approaching each other before they collided.The two simple cases are if they are running in the same direction or opposite direction from each other. For either case, use the conservation of momentum equation to solve: M_total*V_result = M1*V1 + M2*V2
Explanation:
Here are two possible solutions.
Head-on collision: M1=78, V1=8.5, M2=72, V2=-7.5 (that's negative because he's running the other way), M_total = 78+72 = 150, so V_result = (78*8.5 - 72*7.5)/150 = 0.82 m/s. Sanity check, they weigh about the same and so most of their velocity should cancel out.
Running the same way: change the sign of V2 to positive so V_result = (78*8.5 + 72*7.5)/150 = 8.02 m/s. Sanity check, they weigh about the same and the resultant speed is between the two starting velocities.
<em>hope it helps:)</em>
<em>The velocity vector of an object with a centripetal acceleration is never tangent to the circular path is False.</em>
Answer: <em>False</em>
Explanation:
Centripetal acceleration is a feature of objects in uniform circular motion. In that case velocity is along the tangent drawn to the circular path. For an object to be called accelerating its velocity should be variable but speed needn’t.
Even when the speed is constant an object can be accelerating. The direction of velocity of an object in uniform circular motion keeps changing continuously. This change in velocity in uniform circular motion is equal to the centripetal acceleration.