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A lift of mass M is suspended from a cable - AQA - A-Level Physics - Question 15 - 2019 - Paper 1
Question 15
A lift of mass M is suspended from a cable. The lift descends with a downward acceleration, α. A frictional force F acts on the lift. What is the tension T in the c... show full transcript
Worked Solution & Example Answer:A lift of mass M is suspended from a cable - AQA - A-Level Physics - Question 15 - 2019 - Paper 1
Step 1
What is the tension T in the cable?
Answer
To find the tension in the cable, we start by analyzing the forces acting on the lift.
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Forces Acting on the Lift:
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The gravitational force acting on the lift is given by:
where M is the mass of the lift and g is the acceleration due to gravity.
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There is also a frictional force, F, acting against the motion of the lift as it descends.
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Applying Newton's Second Law:
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According to Newton's second law, the net force acting on the lift can be expressed as:
where a is the acceleration of the lift (downward in this case).
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Identifying the Net Force:
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The net force is the difference between the gravitational force and the sum of the frictional force because the lift is accelerating downward:
Rearranging gives us:
Further simplifying this based on the net force gives:
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Conclusion:
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The correct expression for the tension T in the cable, accounting for gravitational force, friction, and acceleration is summarized as:
Evaluating the options provided in the question confirms that this aligns with option D.
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