since child is moving along with the wagon and we need to find the acceleration of child inside that wagon then in this case the system of interest must be child + wagon
System of interest will be the system that is used to find the force or acceleration using Newton's law
Here we have to assume that system on which if we will calculate the forces then the net value of force on that system will help to calculate the unknown quantities
So here our system will be boy + wagon
Answer: Not 100% sure but I believe the answer is B.
Hope this helps! ^^
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<span>To find the wavelength of a neutron can be calculated by using the formula
Wavelength=h/m x v
Where h is planck's constant
m=mass of neutron
v= velocity of the particle
By substituting the given values
Wavelength= 6.63 × 10–34 j s / 1.675 × 10–27 kg x 2 m/s^-1
Wavelength of a neutron=1.979 x 10^-7 m</span>
