Answer:
option a
Explanation:
Size of an atom (diameter) = 10⁻¹⁰ m
There are approximately 10²² atoms in a single drop of water. If they are put in a straight line, the length would be
l = diameter of an atom × number of atoms
l = 10²²× 10⁻¹⁰ m = 10¹² m
Distance between the Sun and the Earth is 1.47 × 10¹¹ m. The calculated length is greater than the distance between the Sun and the Earth.
Thus, option a is correct.
I cannot see all the questions, what is 18,19 and 21? (:
Answer:
Th-234, Pa-234
Explanation:
In alpha decay, 2 protons and 2 neutrons are lost. So U-238 would become Th-234.
In beta decay, one neutron is turned into a proton. So Th-234 would become Pa-234.
To solve this problem we will apply the concepts related to the conservation of kinetic energy and elastic potential energy. Thus we will have that the kinetic energy is

And the potential energy is

Here,
m = mass
v = Velocity
x = Displacement
k = Spring constant
There is equilibrium, then,
KE = PE

Our values are given as,

Replacing we have that


Therefore the speed of the cart is 2.19m/s