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 .
A sound wave is a longitudinal wave
A purple stone because the blue water will distort the red rock and become purple to the eyes
Answer:
Magnetic field is in south west direction .
Explanation:
Let us represent various direction by i , j, k . i representing east , j representing north and k representing vertically upward direction .
magnetic field is represented vectorially as follows
B = B₀ ( - i - j )
In the first case velocity of electron
v = v k
Force = q ( v x B )
= -e [ vk x B₀ ( - i - j ) ]
= evB₀ ( j -i )
Direction of force is north -west .
In the second case velocity of electron
v = vj
Force = -e [ vj x B₀ ( - i - j ) ]
= - evB₀ k
force is downward
In the third case, velocity of electron
v = v( -j +i )
Force = -e [ v( -j +i ) x B₀ ( - i - j ) ]
= 2 evB₀ k
Force is upward.
Answer:
v = 22.54 mph.
Explanation:
Given that,
Distance moved, d = 200 m
Time, t = 19.8 s
We need to find the runner's average speed.
We know that,
1 mile = 1609.34 m
200 m = 0.124 miles
19.8 seconds = 0.0055 h
So,
Speed = distance/time
So, the runner's average speed is 22.54 mph.
