I think the answer is c chemical change
21) Acceleration from D to E: 
22) The acceleration of the bus from D to E is 
Explanation:
21)
The acceleration of an object is equal to the rate of change of velocity of the object. Mathematically:

where
u is the initial velocity
v is the final velocity
t is the time elapsed
In this problem, we want to measure the acceleration of the bus from point D to point E. We have:
- Initial velocity at point D: u = 0
- Final velocity at point E: v = 5 m/s
- Time elapsed from D to E: t = 21 - 16 = 5 s
Therefore, the acceleration between D and E is

22) This question is the same as 21), so the result is the same.
Learn more about acceleration:
brainly.com/question/9527152
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Answer:
Two equal and opposite parallel forces not acting along the same line, form a couple. A couple is always needed to produce the rotation.
For example, turning a key in a lock and turning a steering wheel.
The total work done by the electric field on the charge is given by the scalar product between the electric force acting on the charge and the displacement of the charge:

where the force is F=qE, d=0.556 and

. Using the value of q and E given by the problem, we find