Question

A 4-kg block and a 2-kg block can move on the horizontal frictionless surface. The blocks are accelerated by a+12-N force that pushes the larger block against the smaller one. Determine the force that the 2-kg block exerts on the 4-kg block.
A) -4 N
B) -12 N
C) 0 N
D) +4 N
E) +8 N

Answer 1

Answer:

$F_n = -4 N$

Explanation:

Net external force that exerted on the block is given as

$F_{net} = (m_1 + m_2) a$

here we know that

$F = 12 N$

$m_1 = 4 kg$

$m_2 = 2 kg$

now we have

$12 = (4 + 2) a$

so we have

$a = 2 m/s^2$

now the force exerted by bigger block on smaller block is given as

$F_n = ma$

$F_n = (2 \times 2)$

$F_n = 4 N$

now we know that two blocks will exert equal and opposite force on each other

so here the force exerted by 2 kg block on 4 kg block will be

$F_n = -4 N$