Question

Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s2 what is the tension in the connecting string between the blocks?

Answer 1

Answer:

10 N

Explanation:

from the question we are given

mass of block A = 20 kg

mass of block B = 8 kg

acceleration = 0.5 m/s^2

tension in the connecting string = ?

the tension in the connecting string is acting on block B, and from newtons second law of motion  the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object: F = ma.

therefore the tension acting on the block (T)= mass of the block x acceleration

tension = 20 x 0.5 = 10 N

Answer 2

Answer:

10N

Explanation:

the net horizontal force on both blocks , P = Ma +ma

                                             =(M +m)a

                                              = (20+8)×0.5

                                               =28 × 0.5

                                              =14N

the force acting on the 5kg block = ma

= 8 × 0.5 = 4N

from the attached picture, the pulling force P and the tension on the string are acting in opposite directions and both forces are acting on the 8kg box.

∴ the net resultant force is given as,

P-T=4N

T= P - 4

T=14-4

=10N