# Knocked off my bike in a cycle lane

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#### Profpointy

##### Legendary Member
Impulse requires time, there's no calculation of impulse that ignores time.

It is often calculated with a duration of 0, but it is still calculated with time.

Can you please elaborate why it is not a change of momentum of a period of time?[/QUOT

In your own formula you've mv1-mv2 - so there's no time in there. I accept that the change does take time, but time doesn't affect the value of impulse.

If you divide by time, then you have force which is a different quantity

#### PhilDawson8270

##### Veteran
In your own formula you've mv1-mv2 - so there's no time in there. I accept that the change does take time, but time doesn't affect the value of impulse.

If you divide by time, then you have force which is a different quantity

I think this is getting a little complex for a cycle forum

my formula uses mass and velocity for momentum, velocity is distance over time. So there is time there

But Force is also over time, by the fact its mass * acceleration, which is of course, change of velocity/change in time.

I think, we're both probably saying the same, in a different method. So I'll go with that

#### Profpointy

##### Legendary Member
I think this is getting a little complex for a cycle forum

my formula uses mass and velocity for momentum, velocity is distance over time. So there is time there

But Force is also over time, by the fact its mass * acceleration, which is of course, change of velocity/change in time.

I think, we're both probably saying the same, in a different method. So I'll go with that

I agree with that !

I just remember from my schooldays "impulse is change of momentum" and force is "rate of change of momentum".
Momentum does indeed have a time element in it.

OP
OP

#### annirak

##### Über Member
You guys got my cyclist down post moved to helmets & headphones. Did none of you read the first post? I was trying to keep this about my recovery--some people seemed genuinely interested.

I guess since you couldn't help yourselves and had to throw it into a helmet debate again, it was inevitable, despite my best attempts.

Well, congrats, I'm unsubscribing from my own cyclist down post.

#### theclaud

##### Openly Marxist
You guys got my cyclist down post moved to helmets & headphones. Did none of you read the first post? I was trying to keep this about my recovery--some people seemed genuinely interested.

I guess since you couldn't help yourselves and had to throw it into a helmet debate again, it was inevitable, despite my best attempts.

Well, congrats, I'm unsubscribing from my own cyclist down post.

You're having a tin bath.

#### martint235

##### Dog on a bike
Surely that counts as a flounce?

#### martint235

##### Dog on a bike
I believe that my helmet saved me from serious head trauma. My helmet probably saved my life.

Anyway, I'm taking this opportunity to try and convince people I know who don't wear helmets to start. I kept my shattered CatLike Whisper to show around. I think my next one will be a CatLike Mixino. The £80 I spent on the Whisper was well worth it, considering the job it did. I think the extra for a Mixino will be worth it too.
Errrm doesn't this show that you specifically wanted to provoke a helmet discussion??

#### martint235

##### Dog on a bike
No, it means he wanted his say but not to be questioned on that at all.
Ah. My mistake. Apologies.

#### Licramite

##### Über Member
yes definately in the wrong catagory
not that it would make the slightest difference - mention the word Helmet (or even Hamlet) and in they come
Thou shalt not say helmets or it must mean we must all wear helmets.

if bounced off my head and came out without a head injury I would thank my helmet to. - but I would not put it on this forum.

#### theclaud

##### Openly Marxist
yes definately in the wrong catagory
not hat it would make the slightest diffeence - mention the word Helmet (or even Hamlet) and in they come
Thou shalt not say helmets or it must mean we must all wear helmets.

if bounced off my head and came out without a head injury I would thank my helmet to. - but I would not put it on this forum.

Who are you kidding?

#### Licramite

##### Über Member
not you obviously

#### anothersam

##### SMIDSMe
Many like to wear hats, and that's fine with me.

Like most who don't wear a cycling helmet I'm not anti-helmet, I'm anti- helmets-shoved-down-my-throat-at-every-opportunity-by-the-media (e.g., "the cyclist who was killed when he was crushed under the wheels of the tipper truck wasn't wearing a helmet") and-a-largely-uninformed-public. It can also get a little tiring seeing not-so-subtle hints scattered about, like this sticker I spotted on a train platform:

The OP took a gamble by attaching helmet pics to an ostensibly non-helmet thread; this gamble had failed by post #9:
Ouch! GWS. It's stories like yours that enforce my 'never ride without a lid' rule.

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