You are Here: Home >< A-levels

# Physics SUVAT Question

1. Two cars are travelling towards each other on a single-track road with equal speeds of 35m/s. When they are a distance of 500m apart, they both decide to brake.

a) What minimum equal decelerations would they require to just avoid an accident?

The brakes on one car fail and it continues with the same speed. The other car slows down and at the point of collision it has just stopped.

b) What distances have the two cars travelled when the collision occurs?
c) What time has elapsed?

Any help with working would be really appreciated!
2. a) If they are both travelling at the same speed, and decelerate equally, then they would meet in the middle of the 500m (travel 250m more each). Then you just use the formula : , which can be rearranged to: .

b) Let's say that the car with the working brakes crashes after x metres, so therefore, the car without brakes crashes after travelling 500-x metres.
So therefore you can say that the following equations are both true:
For car with brakes: , u=35, v=0, s=x, which gives
For the car without brakes: , u=35, v=35, s=500-x, which gives
Just solve the two simulataneous equations.
Solving the equations will give you t, which you can use to find x.
3. (Original post by fissionchips)
Two cars are travelling towards each other on a single-track road with equal speeds of 35m/s. When they are a distance of 500m apart, they both decide to brake.

a) What minimum equal decelerations would they require to just avoid an accident?

The brakes on one car fail and it continues with the same speed. The other car slows down and at the point of collision it has just stopped.

b) What distances have the two cars travelled when the collision occurs?
c) What time has elapsed?

Any help with working would be really appreciated!
Part A gives you enough data that you can just plug the values into the v^2=u^2+2as and then you can rearrange to get a.

Part B I am struggling with, would you mind checking to make sure you have put in all the data word for word cause I don't even know what calculation to use for part b.

Part C I think you take away the time it takes for impact when one car is decelerating and the other still travelling at 35ms^-1 away from the larger time where they're both decelerating at the same rate. Not 100% sure cause I haven't done any elapsed time questions before.

Posted from TSR Mobile
4. (Original post by BobBobson)
a) If they are both travelling at the same speed, and decelerate equally, then they would meet in the middle of the 500m (travel 250m more each). Then you just use the formula : , which can be rearranged to: .

b) Let's say that the car with the working brakes crashes after x metres, so therefore, the car without brakes crashes after travelling 500-x metres.
So therefore you can say that the following equations are both true:
For car with brakes: , u=35, v=0, s=x, which gives
For the car without brakes: , u=35, v=35, s=500-x, which gives
Just solve the two simulataneous equations.
Solving the equations will give you t, which you can use to find x.
I never thought to use simultaneous equations, I've never used them before in physics only in maths. That's a tough question.

Posted from TSR Mobile
5. (Original post by RossB1702)
I never thought to use simultaneous equations, I've never used them before in physics only in maths. That's a tough question.

Posted from TSR Mobile
I'm still doing my GCSEs, so I'm not 100% sure it's right but that's how I first thought to do it.
6. (Original post by BobBobson)
I'm still doing my GCSEs, so I'm not 100% sure it's right but that's how I first thought to do it.
You do AVUTS questions in GCSE's ? I did them in Scottish higher physics last year and am now doing advanced higher. Just out of curiosity what's the hardest part of GCSE physics ? I'm sure you're right btw with the simultaneous equation because it looks reasonable and I couldn't find any other method of calculations to do it, you must be pretty good at physics for knowing to do it that way.

Posted from TSR Mobile
7. (Original post by RossB1702)
You do AVUTS questions in GCSE's ? I did them in Scottish higher physics last year and am now doing advanced higher. Just out of curiosity what's the hardest part of GCSE physics ? I'm sure you're right btw with the simultaneous equation because it looks reasonable and I couldn't find any other method of calculations to do it, you must be pretty good at physics for knowing to do it that way.

Posted from TSR Mobile
GCSE Physics isn't hard, it's just a test of memory. The hardest stuff is stuff like nuclear fission / fusion or red shift but that's not really that hard. We learned about kinematic equations in maths, but now they removed that in the new GCSE.
8. (Original post by BobBobson)
GCSE Physics isn't hard, it's just a test of memory. The hardest stuff is stuff like nuclear fission / fusion or red shift but that's not really that hard. We learned about kinematic equations in maths, but now they removed that in the new GCSE.
Yeah, I'm sure AS or A level will challenge you a little when it comes. For now enjoy the smooth sailing. Good luck on your GCSE's!

Posted from TSR Mobile

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: September 20, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Girlfriend studies instead of seeing me

Then says she misses me!

Poll

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets