You are Here: Home >< Maths

# How to resolve unknown mass? watch

1. So for part (a) was to find the tension in the string, which I found was 33.6N, for part (b) do I resolve downwards: mg-T=ma?
Attached Images

2. Make an equation to find the tension in m like you did with 4. Since you already have the value of T you can substitute that in to find m.
3. I didn't read your post properly but I've realised that you've got the equation wrong too. The tension is going in the same direction as the acceleration on m so the tension should be positive. Always draw the directions of acceleration with a double headed arrow so you don't make that mistake.
4. (Original post by AspiringUnderdog)
I didn't read your post properly but I've realised that you've got the equation wrong too. The tension is going in the same direction as the acceleration on m so the tension should be positive. Always draw the directions of acceleration with a double headed arrow so you don't make that mistake.
Okay so
mg+T=ma
m = T/(g+a)
m = 3kg right ?
5. T is in a different direction to mg so it would be T - mg.
When you use F = ma in this case you are resolving a force to find F which in this case is the vertical force.
6. (Original post by AspiringUnderdog)
T is in a different direction to mg so it would be T - mg.
When you use F = ma in this case you are resolving a force to find F which in this case is the vertical force.
Okay thanks

### Related university courses

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: November 5, 2016
The home of Results and Clearing

### 1,376

people online now

### 1,567,000

students helped last year
Today on TSR

### University open days

1. Bournemouth University
Wed, 22 Aug '18
2. University of Buckingham
Thu, 23 Aug '18
3. University of Glasgow
Tue, 28 Aug '18
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