Analyzing Forces on a Car Attached to a Wall with a Rope

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The discussion revolves around a physics problem involving a car attached to a wall by a rope, where the car begins to move when the rope is angled at 5 degrees. Participants analyze the forces acting on both the car and the rope, noting that the car's horizontal acceleration is the primary concern. The absence of friction is highlighted, leading to the conclusion that even a minimal force could theoretically move the car, raising questions about the problem's validity. There is confusion about the application of force equations in different directions, with some participants acknowledging their misinterpretation of the problem's setup. Overall, the problem is critiqued for its poorly constructed premise, suggesting it may be designed to illustrate an absurdity in physics rather than a realistic scenario.
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Homework Statement


A rope is attached to a wall on one end and to a car on the other end. Someone pushes up on the rope and the car starts to move when the rope makes an angle of 5o with the floor. Mcar=2500kg
25z3sas.jpg

Homework Equations


ΣFx=ma
ΣFy=ma

The Attempt at a Solution


Look at the car and the rope separately.

I'm assuming the car has;
ΣFx=ma
ΣFy= 0
and the rope has the opposite;
ΣFx= 0
ΣFy= ma

But I'm not getting anywhere? Am I doing it right?
 
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You seems to be mixing up your x and y directions. (And so was i, because I was trying to read the printing laying on its side.:smile:)
The only force on the car that's accelerating it is horizontal. The trig will tell you what it is at 5o.
But I don't see how there would be any lower limit to the force needed if there is no friction.
 
John_tawil said:
But I'm not getting anywhere? Am I doing it right?
Nothing is accelerating here. (Not yet, anyway.)

Start by identifying the forces acting on the truck.
 
sophiecentaur said:
But I don't see how there would be any lower limit to the force needed if there is no friction.
Oops... I didn't notice that it said no friction. (Missed that when trying to read sideways.)

I don't get the point of the problem. With no friction, you need not be a muscleman to move the truck. A fly could do it.
 
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Doc Al said:
Oops... I didn't notice that it said no friction. (Missed that when trying to read sideways.)

I don't get the point of the problem. With no friction, you need not be a muscleman to move the truck. A fly could do it.
A touch of the "badly written questions' disease, I think.
 
So would you need 1N of force up to push to the left?
 
John_tawil said:
So would you need 1N of force up to push to the left?
If there's no friction, 1microNewton would produce finite acceleration. The question appears to be flawed - or it's angled to make you spot the nonsense aspect of it.
 
sophiecentaur said:
A touch of the "badly written questions' disease, I think.
Indeed. ?:)
 

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