Advanced Forces Question, Forces Inside a Moving Car

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SUMMARY

The discussion focuses on the physics problem involving a mass suspended in a moving car, specifically analyzing the forces acting on the mass as the car accelerates. The key conclusion is that the acceleration of the mass m is equivalent to the acceleration of the car, which can be derived using free body diagrams and the concept of pseudo forces. The correct formula for the acceleration of the car is identified as (E) gtanθ, where θ is the angle the string makes with the vertical. This conclusion is reached by applying Newton's second law, F=ma, and analyzing the forces in two perpendicular directions.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with free body diagrams
  • Knowledge of pseudo forces in non-inertial frames
  • Basic trigonometry, specifically sine and tangent functions
NEXT STEPS
  • Study the application of pseudo forces in accelerating frames of reference
  • Learn how to construct and analyze free body diagrams for complex systems
  • Explore the implications of Newton's second law in non-inertial frames
  • Investigate the relationship between angles and forces in physics problems
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding dynamics in non-inertial reference frames, particularly in relation to forces acting on objects in accelerating vehicles.

Victorzaroni
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Homework Statement



A mass m is suspended by a light string from the ceiling of a moving car of mass M which is accelerating in the horizontal direction. The string makes an angle θ with the vertical as shown below. The acceleration of the car is:
(A) mg/M
(B) gsinø
(C) g/tanø
(D) mg/(m+M)
(E) gtanø

Homework Equations



F=ma

The Attempt at a Solution



I have a free body diagram with g pointing downward along the dotted line and F pointing backwards connecting m and the head of g. I just don't know where to go from here.
 

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Hi Victorzaroni! :smile:

Hint: the acceleration of the mass m is the same as the acceleration of the car. :wink:
 
Identify the constraints .

For the block to be at rest permanently from the car frame, the net force on the block should be zero with respect to the car frame . (Why?)

Draw Free Body Diagram and solve for forces along two perpendicular directions.
Use pseudo force (Why?)(Hint given in above post)
 

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