Question

Find force in newton which mass A exerts on mass B, if B is moving towards right with $3m{s}^{-2}$. Also find mass of A. (All surfaces are smooth, $g=10m{s}^{-2}$)

• A. $5N,\frac{16}{31}kg$
• B. $10N,\frac{31}{16}kg$
• C. $10N,\frac{16}{31}kg$
• D. $5N,\frac{31}{16}kg$

Answer 1

Answer: (A)

$5N,\frac{16}{31}kg$

A can apply force along the normal which has a component along horizontal and vertical.
Its horizontal component is providing the acceleration.

Therefore,
$N\times sin{37}^o=3$
$N=5$.
Now the same magnitude of force will be applied on A by B,
Component of acceleration of both A and B along this normal will be same.
Let $a$ be the acceleration of A vertically downwards then we have,
$a\times cos{37}^o=3\times sin{37}^o$
$a=9/4$
Applying newton's law in the vertical direction,
$mg-N\times cos37=(m\times 9)/4$
$m=16/31kg$