Question

Two blocks A and B with mA = 1.3 kg and mg = 0.88 kg are connected by a string of negligible mass. They rest on a frictionless horizontal surface. You pull on block A with a horizontal force of 7.6 N. (a) Find the magnitude of the acceleration (in m/s2) of the blocks. O m/s2 (b) Determine the tension in N) in the string connecting the two blocks. ON (c) How will the tension in the string be affected if ma is increased? increase decrease O remain the same

Answer 1

Part A.

Using Newton's 2nd law:

F_app = M*a

a = F_app/M

M = total mass of both blocks = mA + mB = 1.3 + 0.88 = 2.18 kg

F_app = Total horizontal Force = 7.6 N

So,

a = 7.6/2.18 = 3.486

a = 3.5 m/sec^2

Part B.

Using Force balance from A block's FBD:

In horizontal direction:

F_net = F_app - T = mA*a

T = F_app - mA*a

T = 7.6 - 1.3*3.486

T = 3.07 N

Or from B block's FBD:

F_net = T = mB*a

T = 0.88*3.486

T = 3.07 N

Part C.

Since

T = F_app - mA*a

So from above expression we can see that if mass of block A is increased, then mA*a will increase, due to which (F_app - mA*a) will decreases, So tension in string will decrease.

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