M1 tow bar question

username2199397

Why is the tensions in the towbar in the opposite directions in part b? Shouldn't it be the other way around?
https://drive.google.com/file/d/1p6twWB8bkrJYh3lEoS-M-6Fr4QoPAHW6/view?usp=drivesdk

OP

Bump

Original post by shohaib712

Why is the tensions in the towbar in the opposite directions in part b? Shouldn't it be the other way around?
https://drive.google.com/file/d/1p6twWB8bkrJYh3lEoS-M-6Fr4QoPAHW6/view?usp=drivesdk

The vehicles are decelerating due to the brakes being applied in the car. The towbar is under compression, not tension, hence the arrows in the diagram.

Reply 3

username2199397

OP

18

Original post by ghostwalker

The vehicles are decelerating due to the brakes being applied in the car. The towbar is under compression, not tension, hence the arrows in the diagram.

Could you explain please?

Reply 4

ghostwalker

17

Original post by shohaib712

Could you explain please?

When a car is pulling a trailer and accelerating, the towbar is under tension, you're effectively trying to pull the two ends of the towbar apart, i.e. stretch it.

When the car is declerating, it's pushing at the trailer to slow it down, and the effect is to try and push the two ends of the towbar together, i.e. compress it. And the force is in the opposite direction.

Reply 5

username2199397

OP

18

Original post by ghostwalker

When a car is pulling a trailer and accelerating, the towbar is under tension, you're effectively trying to pull the two ends of the towbar apart, i.e. stretch it.

When the car is declerating, it's pushing at the trailer to slow it down, and the effect is to try and push the two ends of the towbar together, i.e. compress it. And the force is in the opposite direction.

Oh I see so when the car is slowing down the forces act at the two ends in opposite directions so that they come to a stop. Thank you and could you please help me with how you find out the direction of impulse from collision questions?

I did this question (9b):
https://drive.google.com/file/d/1dlsyzfFpmjrX_UZLPzhUNxHnxV-w3Jr5/view?usp=drivesdk
My working:
https://drive.google.com/file/d/13UrKXj6fEe4uDZm6x6INsp11vsMnq-mV/view?usp=drivesdk

And I tried to find the impulse on particle q by taking the right hand side as positive. but came with an impulse of -4.5um. But the markscheme got 4.5um instead and took the left hand side as positive.