An atom is represented by

here we know that
z = number of protons which gives an idea of positive charge of atom
A = mass number
it is the sum of number of protons and neutrons of an atom which will help us to calculate the mass of the atom
So here mass number A will give us an idea about the mass of atom
so correct answer will be
<em>A) It contains most of the mass.</em>
Answer:
<h2>40 kg</h2>
Explanation:
Find the diagram relating to the question for proper explanation of the question below.
Using the principle of moment
Sum of clockwise moments = Sum of anticlockwise moments
Moment = Force * perpendicular distance
For anti-clockwise moment:
Since the 30 kg moves in the anticlockwise direction according to the diagram
ACW moment = 30 * 1 = 30 kgm
For clockwise moment
If another child sits 0.75 m away from the pivot point on the opposite side, moment of the child in clockwise direction = M * 0.75 = 0.75M (M is the mass of the unknown child).
Equating both moments we have;
0.75M = 30
M = 30/0.75
M = 40 kg
The second child's mass is 40 kg
Answer:
Time to pass the train=0.05 h
How far the car traveled in this time=4.75 Km
Explanation:
We have that the train and the car are moving in the same direction, the difference between the speed of the vehicles is:

We will use this difference in the speed of the car an train to calculate how much time take the car to pass the train. For this we have that the train is 1km long and the car is moving with a speed of 20km/h (we use this value because is the speed that the car have in advantage of the train) then for a movement with a constant speed we have:

Where x is the distance, t is the time and v is the speed. using the data that we have:

This is the time that the car take to pass the train. Now to calculate how far the car have traveled in this time we have to considered the speed of 95Km/h of the car, then:
