Need help calculating the tension in the string of two boxes with friction

The correct equations should be:m1g - T = m1aT - fk = m2aSolving for T in the first equation and substituting into the second equation, we get:m2(m1g - m1a) - fk = m2a^2m1g - m1a - fk/m2 = a^2a = √(m1g - m1a - fk/m2)Substituting the given values, we get:a = √(5*9.8 - 5*1.4 - 0.20*5*9.8/2) = 1.4 m/s^2To find the tension
  • #1
jami8337
26
0

Homework Statement



Two boxes are connected by a cord running over a pulley. Box A sits on a table and has a mass of 5.0 kg while box B hangs
freely and has a mass of 2.0 kg. Box A moves to the right and box B moves
downwards. If the coefficient of kinetic friction between box A and the table is
0.20, what is the acceleration of the system and the tension in the cord? You
may assume that the cord remains taut and does not stretch.

Homework Equations


F=ma
fk=mu*Fn


The Attempt at a Solution


The first part is fine i get 1.4m/s2

then the second part to calculate tension I am lost with what to do:

m1g-T=m1a
T-fk=m2a

where m1= 5kg
m2= 2kg

the answer is supposed to be 17N but when i solve for T i don't get anywhere near that...

thanks
 
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  • #2
You got your m1 and m2 reversed.
 

FAQ: Need help calculating the tension in the string of two boxes with friction

How do you calculate the tension in a string?

The tension in a string can be calculated by using the equation T = m * a, where T is the tension, m is the mass of the object at the end of the string, and a is the acceleration of the object.

What factors affect the tension in a string?

The tension in a string is affected by the weight of the object attached to the string, the angle at which the string is pulled, and any external forces acting on the object.

What is the role of friction in calculating tension in a string?

Friction plays a role in calculating tension in a string when the string is attached to two objects with different masses. In this case, the friction between the string and the objects affects the tension in the string.

How does the angle of the string affect the tension?

The angle of the string affects the tension by changing the direction in which the force is applied. The tension in the string will be greater when the angle is smaller, and it will be smaller when the angle is larger.

Can the tension in a string be greater than the weight of the object?

Yes, the tension in a string can be greater than the weight of the object if there are external forces acting on the object, such as acceleration or friction. In this case, the tension will be equal to the sum of all the forces acting on the object.

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