You are Here: Home >< Physics

# AS physics questions help!! Watch

1. Can some one tell me how i answer the following questions:

1)A spring extends by 9cm when a force of 6 N is applied. The limit of proportionality is not exceeded.
Another identical spring is joined end to end with this spring and a force of 4 N is applied.

What is the extension of the pair of springs?

2) a person weighing 100 N stands on some bathroom scales in a lift. If the scales show a reading of 110 N. What does this describe of the motion of the lift. (e.g moving downwards or upwards, accelerating and declerating??)

3) The acceleration of free fall on a particular planed is 8.0 ms^-2. An object is dropped from a height and hits the ground after 1.5s. From what height was it dropped??

2. 1. It's just proportions. 6N to 9cm so what does 4N give?

2. When the person weighs more than normal the lift is... (try the scenarios with your hands, one hand is person the other the lift floor (it helps me a lot))

3.
3. (Original post by mujahid_e3)
Can some one tell me how i answer the following questions:

1)A spring extends by 9cm when a force of 6 N is applied. The limit of proportionality is not exceeded.
Another identical spring is joined end to end with this spring and a force of 4 N is applied.

What is the extension of the pair of springs?

2) a person weighing 100 N stands on some bathroom scales in a lift. If the scales show a reading of 110 N. What does this describe of the motion of the lift. (e.g moving downwards or upwards, accelerating and declerating??)

3) The acceleration of free fall on a particular planed is 8.0 ms^-2. An object is dropped from a height and hits the ground after 1.5s. From what height was it dropped??

For number 1 yuse Hookes law F=kx for 3 use SUVAT equations
4. (Original post by mujahid_e3)
Can some one tell me how i answer the following questions:

1)A spring extends by 9cm when a force of 6 N is applied. The limit of proportionality is not exceeded.
Another identical spring is joined end to end with this spring and a force of 4 N is applied.

What is the extension of the pair of springs?

2) a person weighing 100 N stands on some bathroom scales in a lift. If the scales show a reading of 110 N. What does this describe of the motion of the lift. (e.g moving downwards or upwards, accelerating and declerating??)

3) The acceleration of free fall on a particular planed is 8.0 ms^-2. An object is dropped from a height and hits the ground after 1.5s. From what height was it dropped??

1 - Firstly, find the spring constant...
Spoiler:
Show

F = Force provided
k = Spring Constant (constant for BOTH identical springs)
Delta L = Extension
Spoiler:
Show

Now;

Because there's 2 springs, the answer is an extension of 6cm per spring, so overall, 12cm.
5. (Original post by soup)
1. It's just proportions. 6N to 9cm so what does 4N give?

2. When the person weighs more than normal the lift is... (try the scenarios with your hands, one hand is person the other the lift floor (it helps me a lot))

3.
Can you explain 1 and 2 to me in bit more detail... If you can give the answer i kinda see where your going..

Thanks for the help soo far
6. (Original post by mujahid_e3)
Can you explain 1 and 2 to me in bit more detail... If you can give the answer i kinda see where your going..

Thanks for the help soo far
For number 1 do what they've told you up above

For 2. The initial force is where m is mass of person. So that will be 100 = mg. But now its is 110 = mg + k. So what is k? k is the unbalanced force (ma). So we say where a is accleration in lift.

Now we need to find a situation where there is acceleration. Up is +ve, down is -ve (since acceleration is a vector)

So accelerating upwards is +ve (accelerating is +ve) times +ve (direction) which is +ve. It's going to give a +ve answer which would be added on to 100. This may explain the increase from 100 to 110
Accelerating downwads is +ve times -ve whice is -ve (direction) . This would be taken away from 100.
Decellerating upwards is -ve (decellerating is -ve) times +ve whice is -ve. This would be taken away from 100.
Decellerating downwards is -ve times -ve which is +ve. It's going to give a +ve answer which would be added on to 100. This may explain the increase from 100 to 110
7. (Original post by soup)
For number 1 do what they've told you up above

For 2. The initial force is where m is mass of person. So that will be 100 = mg. But now its is 110 = mg + k. So what is k? k is the unbalanced force (ma). So we say where a is accleration in lift.

Now we need to find a situation where there is acceleration. Up is +ve, down is -ve (since acceleration is a vector)

So accelerating upwards is +ve (accelerating is +ve) times +ve (direction) which is +ve. It's going to give a +ve answer which would be added on to 100. This may explain the increase from 100 to 110
Accelerating downwads is +ve times -ve whice is -ve (direction) . This would be taken away from 100.
Decellerating upwards is -ve (decellerating is -ve) times +ve whice is -ve. This would be taken away from 100.
Decellerating downwards is -ve times -ve which is +ve. It's going to give a +ve answer which would be added on to 100. This may explain the increase from 100 to 110

so for 1 do you just find the K? if not what do i do?
8. (Original post by mujahid_e3)
so for 1 do you just find the K? if not what do i do?
Yes just do what Ian. said
9. (Original post by soup)
1. It's just proportions. 6N to 9cm so what does 4N give?

2. When the person weighs more than normal the lift is... (try the scenarios with your hands, one hand is person the other the lift floor (it helps me a lot))

3.
Sorry to keep bothering you, but how would you actually do q3? Because you dont have u , you only have a and t? So please explain

Thanks
10. (Original post by Ian.)
1 - Firstly, find the spring constant...
Spoiler:
Show

F = Force provided
k = Spring Constant (constant for BOTH identical springs)
Delta L = Extension
Spoiler:
Show

Now;

Because there's 2 springs, the answer is an extension of 6cm per spring, so overall, 12cm.
Thanks for that.. You helped alot.. Could you explain q3?? please

Thanks
11. (Original post by mujahid_e3)
Sorry to keep bothering you, but how would you actually do q3? Because you dont have u , you only have a and t? So please explain

Thanks
The object was dropped so the initial velocity was zero
12. (Original post by mujahid_e3)
Sorry to keep bothering you, but how would you actually do q3? Because you dont have u , you only have a and t? So please explain

Thanks
u = 0
The object was dropped.
13. Thanks everybody!

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:
Updated: December 18, 2010
Today on TSR

### Cambridge interview invitations

Has yours come through yet?

### Official Oxford interview invite list

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.