I'm gonna have to assume the girl is on the right side and boy on left.
The net force is the sum of all forces on an object (includes negatives).
Let's say the force of the boy is variable <em>b</em>. Use the formula F = ma.
<em>b </em>+ 3.5 = 0.2(2.5)
This is now simple algebra. Solve to get that <em />the boty is exerting a force of -3N to the left.
The recoil velocity of the astronaut is -0.070 m/s
Explanation:
We can solve this problem by using the principle of conservation of momentum: in fact, in absence of external forces, the total momentum of the astronaut-wrench system must be conserved.
At the beginning, their total momentum is zero:
(1)
Later, after the astronaut throws the wrench, the total momentum is
(2)
where
m = 0.725 kg is the mass of the wrench
v = 13.8 m/s is the velocity of the wrench
M = 143 kg is the mass of the astronaut
V is the recoil velocity of the astronaut
Since momentum is conserved, (1) = (2), and so we can find V:

Learn more about momentum:
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I think is True! Is the best answer. Because the trumpet it make them sounds like the lips with the musician and it vibrate.
To solve this problem we will apply the concepts related to wavelength, as well as Rayleigh's Criterion or Optical resolution, the optical limit due to diffraction can be calculated empirically from the following relationship,

Here,
= Wavelength
d= Diameter of aperture
= Angular resolution or diffraction angle
Our values are given as,

The frequency of the sound is 
The speed of the sound is 
The wavelength of the sound is

Here,
v = Velocity of the wave
f = Frequency
Replacing,


The diffraction condition is then,

Replacing,

d = 0.24 m
Therefore the diameter should be 0.24m
Given :
An object 50 cm high is placed 1 m in front of a converging lens whose focal length is 1.5 m.
To Find :
the image height (in cm).
Solution :
By lens formula :

Here, u = - 100 cm
f = 150 cm

Now, magnification is given by :

Therefore, the image height is 3 m or 300 cm.