<u>Harmful</u><u />
-causes heat; if it's not used correctly, it can cause injury
-when falling, the friction between your knee/leg and the ground can cause scrapes
<u>
</u><u>Helpful</u><u />
-helps stop the bike, the brakes rub against the tire which slows it down to a stop
-it can also help move the bike; the chains rub against tires which accelerate the bike
Answer:
water
Explanation:
coz out of the choices water is the only one that is not an element.
water formula is H2O
Answer:
D
Explanation:
The gravity is pushing the water downward so Wayne could go down but the water is pushing Wayne to go up which would make him float.
Answer:
Stationary
20N
Explanation:
From the graph, we see that the body traveling is on a fixed position. Therefore, it is a stationary body.
The graph given is a position - time curve.
This curve depict a body changing position with given time.
Since the line of the curve is on a single position, the body is not changing position with the passage of time therefore, it is a stationary object.
B. 20N
From Newton's third law of motion we understand that "action and reaction force are equal but oppositely directed".
Since the person is exerting a force of 20N on the balance.
So, the reaction force by the balance is 20N upward.
Answer:

and

Explanation:
See attached figure.
E due to sphere
E due to particule
(1)
according to the law of gauss and superposition Law:
; electric field due to the small sphere with r1=R/4


then:
(2)
on the other hand, for the particule:

⇒
(3)
We replace (2) y (3) in (1):


--------------------
if R<x<2R AND 

remember that 
then:

solving:


but: R<x<2R
so : 