You are Here: Home >< Maths

# M1 friction question involving rough wire watch

Announcements
1. hi I would like to know why the normal reaction force is acting in the direction shown in the diagram. Why wouldnt R act in the direction opposite to the one in the diagram? I get why F acts in that way by the way. Thanks!
2. (Original post by coconut64)
hi I would like to know why the normal reaction force is acting in the direction shown in the diagram. Why wouldnt R act in the direction opposite to the one in the diagram? I get why F acts in that way by the way. Thanks!
This is how I think of it, which then doesn't guarantee that it's correct, is that the wire needs to pull back in the opposite direction in order to stay stationary, as otherwise it would be massive pulled to the right

For example, if I held a ball in my hand, the ball has mass so pushes downwards, in order for my hand to remain upright and not helplessly fall to the ground it needs to exert a force upwards to maintain equilibrium
3. (Original post by KaylaB)
This is how I think of it, which then doesn't guarantee that it's correct, is that the wire needs to pull back in the opposite direction in order to stay stationary, as otherwise it would be massive pulled to the right

For example, if I held a ball in my hand, the ball has mass so pushes downwards, in order for my hand to remain upright and not helplessly fall to the ground it needs to exert a force upwards to maintain equilibrium
Ah ! That makes sense and your analogy seems to work in other similar questions as well. Thanks, thats quite clever.
4. (Original post by coconut64)
Ah ! That makes sense and your analogy seems to work in other similar questions as well. Thanks, thats quite clever.
No problem
5. there must be a force to the left as the tension has a component to the right. as ^^ said.
6. (Original post by KaylaB)
This is how I think of it, which then doesn't guarantee that it's correct
It is. :-)

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: April 6, 2016
Today on TSR

### Lied on my UCAS

And my school told me not to change it

### University open days

• University of the West of England, Bristol
Wed, 23 Jan '19
• University of East London
Wed, 23 Jan '19
• University of Gloucestershire
School of Education Open Day Postgraduate
Wed, 23 Jan '19
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