Answer:
The runner's acceleration was 
Explanation:
<u>Constant Acceleration Motion</u>
It's a type of motion in which the velocity of an object changes by an equal amount in every equal period of time.
Being a the constant acceleration, vo the initial speed, vf the final speed, and t the time, the following relation applies:

Solving for a:

The runner speeds up from vo=5 m/s to vf=9 m/s in t=4 seconds, thus:


The runner's acceleration was 
Answer: Gravitational force and drag force
Explanation:
For a snowboard jumper in the air, two forces would be acting. One in the downward direction- the gravitational pull and second in the opposite direction to the motion, the drag force due to air. If the snowboard jumper jumps in the air at a certain angle with the horizontal. The forces are written as the sum of vertical and horizontal components. Hence, for the modeling the motion, gravitational force and drag force are important,
When the surface of the comb rubs on your hair, the comb is electrically charged. When the comb comes close to the paper, the charge on the comb causes charge separation on the paper bits. Since paper is neutral, positive and negative charges are equivalent. The charge on the comb charges the area of the bit of paper nearest the comb to the opposite. Thus, the bits of paper become attracted to the comb.
The student's claim did not follow the scientific method of discovery, hence, it is an opinion not a scientific claim.
<h3>What is the scientific method?</h3>
The scientific method is a procedure employed by scientific towards understanding the world around them as well giving explanation for phenomena in the natural world.
The scientific method involves:
- observations
- asking questions
- putting forward a hypothesis
- testing the hypothesis through experiments
- analyzing results of the experiments and drawing conclusions
- establishing a theory.
Since the student in question just put forward an opinion without testing it out using the scientific method, the statement is not a scientific claim.
Learn more about scientific method at: brainly.com/question/17216882