Original post by 1234kelly
Can someone please explain to me why the tension in the tow bar is a thrust force? I thought it was a tension but the markscheme says it’s a thrust force.
I get ma as being 750 and resolved weight-friction as 650 so there must be a force of 100 N pulling down the slope so the tow bar must be in tension. So accelerating the trailer and re tarding the car.
The only thing I can think why they may say its a thrust is because of the action it has on the trailer, rather than being the force in the tow bar. But Id say the tow bar is in tension.
(edited 1 year ago)
Reply 2
Original post by 1234kelly
Can someone please explain to me why the tension in the tow bar is a thrust force? I thought it was a tension but the markscheme says it’s a thrust force.
When the car and trailer are travelling uphill, I think we are safe to assume that the car is ahead (uphill) of the trailer. When the car and trailer start to accelerate in the downhill direction, they may still be travelling uphill, with the car still uphill of the trailer. In that case, there will be thrust, not tension, in the towbar.
Original post by mqb2766
I get ma as being 750 and resolved weight-friction as 650 so there must be a force of 100 N pulling down the slope so the tow bar must be in tension. So accelerating the trailer and re tarding the car.
The only thing I can think why they may say its a thrust is because of the action it has on the trailer, rather than being the force in the tow bar. But Id say the tow bar is in tension.
The only thing I can think why they may say its a thrust is because of the action it has on the trailer, rather than being the force in the tow bar. But Id say the tow bar is in tension.
Thank you for taking the time to answer !
Original post by 1234kelly
Thank you for taking the time to answer !
Can you upload the full question and the full mark scheme? The "OR" part in the posted mark scheme refers to a 2m/s^2 acceleration which seems unrelated to the posted parts. Also where is the question from?
(edited 1 year ago)
Original post by mqb2766
Can you upload the full question and the full mark scheme? The "OR" part in the posted mark scheme refers to a 2m/s^2 acceleration which seems unrelated to the posted parts. Also where is the question from?
Original post by old_engineer
When the car and trailer are travelling uphill, I think we are safe to assume that the car is ahead (uphill) of the trailer. When the car and trailer start to accelerate in the downhill direction, they may still be travelling uphill, with the car still uphill of the trailer. In that case, there will be thrust, not tension, in the towbar.
Thank you do much for answering! But quick question:
-wait so when the question state that they accelerate down the slope I can’t just assume that car and trailer have flipped position and so the car is still ahead of the trailer when they’re accelerating down hill like I have in my diagram?
-also what do you mean by When the car and trailer start to accelerate in the downhill direction, they may still be travelling uphill? How is that possible? Calculation wise do I just flip the direction that I am taking as positive ?
The 2m/s^2 in the OR part of the mark scheme suggests it may be an edited question/mark scheme. Though Id have done the question as youve done so car pulling the trailer down the slope. Gravity - friciton produces a net acceleration of 1.3 m/s^2 of the trailer so the tow bar must be providing an additional thrust or driving force or equivalently the trailer drags the tow bar (force pair). So the tow bar must be in tension.
(edited 1 year ago)
Reply 8
Original post by 1234kelly
Thank you do much for answering! But quick question:
-wait so when the question state that they accelerate down the slope I can’t just assume that car and trailer have flipped position and so the car is still ahead of the trailer when they’re accelerating down hill like I have in my diagram?
-also what do you mean by When the car and trailer start to accelerate in the downhill direction, they may still be travelling uphill? How is that possible? Calculation wise do I just flip the direction that I am taking as positive ?
-wait so when the question state that they accelerate down the slope I can’t just assume that car and trailer have flipped position and so the car is still ahead of the trailer when they’re accelerating down hill like I have in my diagram?
-also what do you mean by When the car and trailer start to accelerate in the downhill direction, they may still be travelling uphill? How is that possible? Calculation wise do I just flip the direction that I am taking as positive ?
Say the car and trailer are travelling uphill at 15ms^-1. They could then start to decelerate at 1.5ms^-2, which is the same as accelerating in the downhill direction (while still travelling uphill for the ten second it would take for the uphill velocity to reduce to zero).
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