Answer:
option (c) is correct
Explanation:
Half life of a substance is the time in which the element becomes half of is initial value.
half life, T = 8 days
Amount remaining, N = 10 % of original value
Let the original value is No.
N = 10% of No
N = 0.1 No
Let the time taken is t and the decay constant is λ.
The relation between the decay constant and the half life is given by

Us the equation of radioactivity



Taking natural log on both the sides, we get
0.08664 t = 2.303
t = 26.6 days
Answer:
a)

b) 
Explanation:
The net force on the car must produce the centripetal acceleration necessary to make this circle, which is
. At the top of the circle, the normal force and the weight point downwards (like the centripetal force should), while at the bottom the normal force points upwards (like the centripetal force should) and the weight downwards, so we have (taking the upwards direction as positive):

Which means:

The limit for falling off would be
, so the minimum speed would be:

Answer:
right
Explanation:
its on ur right because a compass goes N E S W in a clockwise order, hope this helps !! :)