Answer:
Let No be initial no of atoms
N = N0 / 2 after 1 half-life
N = N0 / 4 after 2 half-lives
So after 2 half-lives 20 of the 80 atoms remain
Answer: The cylinder
Explanation:
Among all other solid shapes, the sphere has the smallest area for a given volume.
By experiment, the ratio of the radius of a sphere to a cylinder of equal volume is less than 1.
Recall;
That the Rate of transfer of convective heat (Q) = h × A ×change in temperature.
Where ,
h= the co efficient of convective heat transfer
A= the cross sectional area.
As such, since the sphere has a smaller surface area relative to the cylinder, the sphere transfers heat slower than the cylinder.
Therefore, if the sphere and cylinder are exposed to convection in the same environment, then, the cylinder cools faster.
PS; the more the Area, the higher the rate of heat transfer and vice versa.
Answer:
Ans is 200 J
Explanation:
Given: Force = 20N
Distance = 10m
Work done = Force * displacement
= 20 * 10
= 200 J
Answer:
Tangential speed, v = 2.64 m/s
Explanation:
Given that,
Mass of the puck, m = 0.5 kg
Tension acting in the string, T = 3.5 N
Radius of the circular path, r = 1 m
To find,
The tangential speed of the puck.
Solution,
The centripetal force acting in the string is balanced by the tangential speed of the puck. The expression for the centripetal force is given by :



v = 2.64 m/s
Therefore, the tangential speed of the puck is 2.64 m/s.