Question

Two blocks of mass 10 kg and 40 kg are connected by a string. The 40 kg block is pulled by a
constant force of 60 N. Find the frictional force acting on 10 kg block? (g = 10 m/s2)
10 kg
40 kg
F=60 N
u=0.3
(B) 20 N
u=0.2
(C) Zero
(A) 10 N
(D) 30 N​

Answer 1

The two blocks of mass different are

• Let m₁= 10Kg
• Let m₂=40Kg
• They are attached by string and being pulled by the constant force 60 N acting on 40 Kg.
• We need to find the frictional force acting on 10 Kg
• The normal force acting on m₁ is N₁=10×10=100 N
• The normal force acting on m₂ is N₂=40×10=400 N
• So, now the frictional force acting on m₁=N₁ц=100×0.3
• Therefore the frictional force on 10 Kg block is 30 N
• The option D is correct

Answer 2

Given:

mass of block 1 is = 10 kg  

Mass of block 2 is = 40 kg

Force F = 60kg

  Acceleration due to gravity g = 10 m/S2

And  coefficient of friction u = .3 (unit less)

To Find:

frictional force F on 10 kg block

Solution:

          Using free body diagram of both the block

We find that frictional force on block of 10 kg is

      F=umg  

which is coefficient of friction × normal reaction

    Normal reaction N = mg

So F = 10$\times$0.3

Thus by solving we get,

   F = 30 $kgm/s^2$

Thus we get frictional force as F = 30 $kgm/s^2$