Question

Two blocks of masses 8kg and 2kg respectively lie on a smooth horizontal surface in contact with one other.They are pushed by a horizontally applied force of 15N.calculate the force exerted on the 2kg mass

Answer 1

f=M2F÷M1+M2

we get on substituting

3N

Answer 2

case1 : when force is applied on block of mass 8kg.

Let N is normal reaction between the blocks.

then, for 8 kg block : F - N = Ma ...(1)

for 2kg block : N = ma .....(2)

from equations (1) and (2),

F - ma = Ma

F = (m + M)a

so, a = F/(m + M) = 15N/(2g + 8kg) = 1.5 m/s²

so, force exerted on the 2kg block = ma

= 2kg × 1.5 m/s² = 3N

case2 : when force is applied on the block of mass 2kg.

then, for 2kg block : F - N = ma ....(1)

for 8kg block : N = Ma .....(2)

from equations (1) and (2),

F = (m + M)a ,

so, a = F/(m + M) = 1.5 m/s²

now force exerted on the 2kg mass = ma

= 2kg × 1.5 m/s² = 3N

we see, in both conditions force exerted on the 2kg mass is 3N. so, answer should be 3N