An epidemiologist is a doctor who counteracts mass infections (epidemics, pandemics), organizes the treatment and prevention of the spread of epidemics.
Answer:
J = 1800 kg-m/s
Explanation:
Given that,
Mass of a boy, m = 150 kg
Initial velocity of a boy, u = 12 m/s
Finally, it stops, v = 0
We need to find the impulse is required to produce this change in momentum. We know that impulse is equal to the change in momentum. So,

So, the impulse is equal to 1800 kg-m/s
Answer:
Frequency, 
Explanation:
Wavelength of a light wave is 450 nm. It is required to find the frequency of this light wave. The speed of light is given by c. So,

f is the frequency of this light

So, the frequency of this light is
.
The recoil velocity of cannon is (4) 5.0 m/s
Explanation:
We can find the recoil velocity from the law of conservation of momentum.
The recoil velocity is velocity of body 2 after release of body 1, i.e. velocity of cannon after release of clown.
Let v2 be cannon's velocity, v1 be clown's velocity given = 15 m/sec
m1 be clown's mass = 100kg and m2 be cannon's mass given = 500kg.
So recoil velocity of cannon v2 is given by,
v2 = -(m1÷m2)v1
v2 = -(100÷500)15
v2 = -5 m/s
where the minus sign refers to the direction of cannon's recoil velocity being opposite to that of clown.
Hence, option (4)5.0 m/s is the correct answer.
Here in order to find out the distance between two planes after 3 hours can be calculated by the concept of relative velocity

here
speed of first plane is 700 mi/h at 31.3 degree


speed of second plane is 570 mi/h at 134 degree


now the relative velocity is given as


now the distance between them is given as



so the magnitude of the distance is given as

miles
so the distance between them is 2985.6 miles