A particle of mass 2 kg is connected to another particle of mass 3 kg by a taut light inelastic string which passes over a smooth light pulley at the edge of a rough horizontal table - Leaving Cert Applied Maths - Question 4 - 2013
Question 4
A particle of mass 2 kg is connected to another particle of mass 3 kg by a taut light inelastic string which passes over a smooth light pulley at the edge of a rough... show full transcript
Worked Solution & Example Answer:A particle of mass 2 kg is connected to another particle of mass 3 kg by a taut light inelastic string which passes over a smooth light pulley at the edge of a rough horizontal table - Leaving Cert Applied Maths - Question 4 - 2013
Step 1
Show on separate diagrams the forces acting on each particle.
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Answer
For the 2 kg mass on the table:
Weight, W1=2g
Normal force, R
Frictional force, f=21R
Tension, T in the string.
For the 3 kg mass hanging:
Weight, W2=3g
Tension, T in the string.
Step 2
Find the common acceleration of the particles.
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Answer
Using Newton’s second law for the 3 kg mass:
3g−T=3a
For the 2 kg mass:
T−21R−2g=2a
Since R=2g−f and f=21R, substituting gives:
T+41R=2a
Combining and solving these equations leads to:
a=52g=4m/s2.
Step 3
Find the tension in the string.
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Answer
Substituting the acceleration back into the equations gives:
Using T=3g−3a leads to:
T=3(10)−3(4)=18N.
Step 4
Find the common acceleration of the particles.
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Answer
For the 6 kg mass:
6gcos(30∘)−T=6a
For the 2 kg mass:
T−2g=2a
Substituting and simplifying gives:
g=8 leads to a=810=1.25m/s2.
Step 5
Find the tension in the string.
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Answer
Using the calculated acceleration in:
T=2g+2a results in:
T=22.5N.
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