Answer:
(a) the blocks all had different masses.
Explanation:
The surface is smooth, therefore coefficient of friction is tending to zero.
Forces for each blocks varied from 6N to 8N to 7N to 5N
The blocks were made of different materials and different materials are going to have varying weight for the same size of block.
The startling answer is:
The bacteria ate the agar and reproduced (made more bacteria). There are so many of them now that you can see the blob of them.
Answer:
Explanation:
Given
Initial linear speed 
initial angular velocity 
Speed after 4.1 s is 

using 
where
is angular acceleration

i.e. clockwise
(b)angular displacement




Remember, Your electric field lines drawn from positive charge (protons) and goes to negative charge (electron)
So, Your Answers would be:
15) B) Positive
16) A) Negative
17) B) Positive
18) A) Negative
19) B) Positive
20) B) Positive
Hope this helps!