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The answers false I believe
Answer:
Explanation:
Let the forward displacement is taken is positive, and the backward displacement is taken is negative.
first displacement = + 18 cm
second displacement = - 6 cm
third displacement = - 12 cm
net displacement = 18 - 12 - 6 = 0 cm
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:

where;
= final velocity = 0
= initial velocity = 60 km/h = 16.67 m/s
= acceleration
= distance
First all of, because acceleration is given in m/s and not km/h, you need to convert 60km/h to m/s. Our conversion factors here are 1km = 1000m and 1h = 3600s

Solve for a;

Begin by subtracting 

Divide by 2d

Now plug in your values:



If you're wondering why I calculated acceleration first is because in order to find force, we need 2 things: mass and acceleration.

m = mass = 900kg
a = acceleration = -2.78m/s

It's negative because the force has to be applied in the opposite direction that the car is moving.