Answer:
the height of the cliff is equal to 108.241 m
Explanation:
given,
initial speed of the stone horizontally = 9 m/s
vertical speed of the stone = 0 m/s
time taken of the trajectory = 4.7 s
using equation of motion
s = 108.241 m
hence, the height of the cliff is equal to 108.241 m
The weight of the needle is 0.007 N.
Explanation:
Surface tension is the force acting on the surface of any fluid or film due to the attractive forces on the surface of them. So it is measured as force acting per unit effective length on the surface. The effective length is the distance or the length which is in contact with the surface.
For example, in the present case, the needle can be in contact with the water body from both sides of the needle. So effective length of the needle will be 2 times the length of the needle. Then the surface tension on the water due to the needle will be
As the length of the needle is given as 5 cm = 0.05 m and the surface tension of water is given as 0.07 N/m, then the weight of the needle will be equal to the force applied by the needle.
So, the weight of the needle is 0.007 N.
The process of becoming a scientific theory
If enough evidence accumulates to support a hypothesis, it moves to the next step — known as a theory — in the scientific method and becomes accepted as a valid explanation of a phenomenon.