Question

Two bodies P and Q of masses 10kg and 15kg respectively are connected by a light inextensible string.
mass 15kg is at free fall pulling mass 10kg.
P is placed on a tough surface of the coefficient of friction, 0.5. if the acceleration due to gravity is 10m/s², calculate the magnitude of the:
(i) normal reaction on P
(ii) frictional force between P and the surface
(iii) tension in the string
(iv) force which causes P and Q to accelerate
(v)common acceleration of P and Q​

Answer 1

Explanation:

Horizontal force,F=600 N

Mass of body A, m

1

=10 kg

Mass of body B, m2=20 kg

Total mass of the system, m=m1+m2=30 kg

Using Newtons second law of motion, the acceleration (a) produced in the system can be calculated as:

F=ma

a=

m

F

=

30

600

=20m/s

2

When force F is applied on body A:

The equation of motion can be written as: F−T=m

1

a

T=F−(m

1

)a

=600−10×20=400 N (i)

When force F is applied on body B:

The equation of motion can be written as:

F−T=m

2

a

T=F−(m

2

)a

T=600−20×20=200 N (ii)

which is different from value of T in case (i). Hence our answer depends on which mass end, the force is applied.