You are Here: Home >< Maths

# M2 help watch

1. http://www.ocr.org.uk/Images/144604-...echanics-2.pdf

Q8ii.

Can someone explain what the question is asking. Does the friction have to be greater than the reaction for it not to slip? idk
2. (Original post by Super199)
http://www.ocr.org.uk/Images/144604-...echanics-2.pdf

Q8ii.

Can someone explain what the question is asking. Does the friction have to be greater than the reaction for it not to slip? idk
At the max possible speed, friction will act in the opposite direction to previously (so towards V) since the particle will want to spin out of the circle and up the slope.

Someone can probably explain that in more mathematically correct terms but that's kind of the idea behind it.
3. (Original post by tinkerbella~)
At the max possible speed, friction will act in the opposite direction to previously (so towards V) since the particle will want to spin out of the circle and up the slope.

Someone can probably explain that in more mathematically correct terms but that's kind of the idea behind it.
Sorry I don't get why friction is down, even though you have sort of explained :/
4. (Original post by Super199)
Sorry I don't get why friction is down, even though you have sort of explained :/
(Original post by tinkerbella~)
Someone can probably explain that in more mathematically correct terms but that's kind of the idea behind it.
Reaction force is perpendicular to the surface, friction is perpendicular to reaction. So friction acts parallel to the surface. In the first bit of the question, the friction acts upwards because the natural tendency of the particle is to slip down the slope.

In the last part of the question, you want to maximise the angular speed with the constraint that the particle doesn't slip. That is, if you increase the speed beyond this maximum angular speed, the particle will spiral or 'slip' upwards. Friction opposes motion and acts down the slope instead.

Furthermore, you'll want to use the limiting value of friction in order to maximise centripetal acceleration and hence maximise angular velocity.

tl;dr:

Minimum angular speed occurs when the particle is going to slip downwards, because if it goes any slower it falls down the slope so friction acts upwards.

Maximum angular speed occurs when the particle is going to slip upwards, because if it goes any faster it flies up the slope, so friction acts downwards.

Friction opposes motion.
5. (Original post by Zacken)
Reaction force is perpendicular to the surface, friction is perpendicular to reaction. So friction acts parallel to the surface. In the first bit of the question, the friction acts upwards because the natural tendency of the particle is to slip down the slope.

In the last part of the question, you want to maximise the angular speed with the constraint that the particle doesn't slip. That is, if you increase the speed beyond this maximum angular speed, the particle will spiral or 'slip' upwards. Friction opposes motion and acts down the slope instead.

Furthermore, you'll want to use the limiting value of friction in order to maximise centripetal acceleration and hence maximise angular velocity.

tl;dr:

Minimum angular speed occurs when the particle is going to slip downwards, because if it goes any slower it falls down the slope so friction acts upwards.

Maximum angular speed occurs when the particle is going to slip upwards, because if it goes any faster it flies up the slope, so friction acts downwards.

Friction opposes motion.
Brilliant! Got it
6. (Original post by Super199)
Brilliant! Got it
No problem.

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: May 17, 2016
Today on TSR

### Tuition fees under review

Would you pay less for a humanities degree?

### Can I get A*s if I start studying now?

Discussions on TSR

• Latest
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

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