As we know f is inversely proportion to time so its frequency is 1/4 Hz
Answer:
(a) 
(b) 1.71
Explanation:
(a) The difference in the times of travel in the two case = 
This difference is the time in the transparent material. With a thickness of 35.0 cm, the speed in the material is

(b) The refractive index of the material is the ratio of the velocity of light in vacuum to its velocity in the material. Using speed of light in vacuum as
, the refractive index,
, is

Answer:250N
Explanation:
Spring constant=500N/m
Extension=0.5m
Weight=spring constant x extension
Weight=500 x 0.5
Weight=250
Weight is 250N
QUICK ANSWER
The collision between two gas molecules or billiard balls can be approximated as elastic collisions. Elastic collisions are exchanges of kinetic energy between two bodies having different reference frames in which the total kinetic energy of the two bodies after collision is equal to the energy before collision.'
a friction force 10 N less than the applied force, a normal force equal to the gravtiational force