The displacement ........................
Placing elements into columns, groups, rows and periods that share certain properties. properties such as gas, solid and liquid determine an element physical state at room temperature.
Answer:
a. speed, v = 0.97 c
b. time, t' = 20.56 years
Given:
t' = 5 years
distance of the planet from the earth, d = 10 light years = 10 c
Solution:
(a) Distance travelled in a round trip, d' = 2d = 20 c = L'
Now, using Length contraction formula of relativity theory:
(1)
time taken = 5 years
We know that :
time = 
5 =
(2)
Dividing eqn (1) by v on both the sides and substituting eqn (2) in eqn (1):
Squaring both the sides and Solving above eqution, we get:
v = 0.97 c
(b) Time observed from Earth:
Using time dilation:


Solving the above eqn:
t'' = 20.56 years
Friction stole the book's kinetic energy, and turned it into heat energy ... which blew away in the breeze.