Answer:
I think
D : Hydrogen gas has two atom , and oxygen has one atom
Before coming into conclusion first we have to understand both scalar and vector .
A scalar quantity is a physical quantity which has only magnitude for it's complete specification.
A vector quantity is that physical quantity which not only requires magnitude but also possesses direction for it's complete specification.
So the most important factor that differentiate vector from scalar is the direction.
As per the question the student is doing an experiment where he is recording the data obtained during the process.
In order to arrange them in data table, he should ask about the direction of the quantity under consideration.
Hence the correct option is the third option(C)i.e does the measurement include direction?
Here when car in front of us applied brakes then it is slowing down due to frictional force on it
So here we can say that friction force on the car front of our car is given as

So the acceleration of car due to friction is given as



now it is given that


so here we have


so the car will accelerate due to brakes by a = - 8.52 m/s^2
Answer:

Explanation:
From the question we are told that
Weight of fireman 
Pole distance 
Final speed is 
Generally the equation for velocity is mathematically represented as

Therefore Acceleration a
Generally the equation for Frictional force
is mathematically given as



Therefore

Answer:
3secs
Explanation:
Given the following parameters
height H= 81.3m
Velocity v = 12.4m/s
Required
Time it take to reach the ground
Using the equation of motion
H = ut+1/2gt²
81.3 = 12.4t + 1/2(9.8)t²
81.3 = 12.4t + 4.9t²
4.9t² + 12.4t - 81.3 = 0
Using the general formula to find t
t = -12.4±√12.4²-4(4.9)(-81.3)/2(4.9)
t = -12.4±√153.76+1593.48/2(4.9)
t = -12.4±√1747.24/9.8
t = -12.4+41.8/9.8
t = 29.4/9.8
t = 3secs
Hence it took 3secs to reach the ground