How many times did the original sample lose 50% of its radioactivity ?
-- Start with. . . . . . . . . . . . 12 grams.
-- Lose half of it once. . . . . . 6 grams left.
-- Lose half of it again . . . . . 3 grams left.
-- Lose half of it again . . . . . 1.5 grams left.
-- Lose half of it again . . . . . 0.75 gram left.
-- How many times did it lose half ? 4 times.
-- How long does it take to lose half ? 4.5 days.
(That's why it's called the 'half-life'.)
-- How long did it take to lose half, 4 times ?
(4 x 4.5 days) = 18 days .
They are malleable and lustrous, and can conduct both electricity and thermal heat
Answer:
The time of flight of the ball is 1.06 seconds.
Explanation:
Given 

Also, 

Let us say the velocity in the x-direction is
and in the y-direction is
. And acceleration in the x-direction is
and in the y-direction is
.
Also,
is distance covered in x and y direction respectively. And
is the time taken by the ball to hit the backboard.
We can write
. Where
is velocity of ball.
Now,


Also,
.
Plugging this value in


So, the time of flight of the ball is 1.06 seconds.
Answer:
The kinetic energy of the mass at the instant it passes back through the equilibrium position is 0.06500 J.
Explanation:
Given that,
Mass = 2.15 kg
Distance = 0.0895 m
Amplitude = 0.0235 m
We need to calculate the spring constant
Using newton's second law

Where, f = restoring force


Put the value into the formula


We need to calculate the kinetic energy of the mass
Using formula of kinetic energy

Here, 

Here, 


Put the value into the formula


Hence, The kinetic energy of the mass at the instant it passes back through the equilibrium position is 0.06500 J.