x Turn on thread page Beta
 You are Here: Home >< A-levels

# Mechanics help watch

1. I need some help.

"A particle of mass m kg slides down a smooth inclined plane with an acceleration of 2 ms^-2. Find the inclination of the plane to the horizontal."

I know that I can use F=ma to calculate the mass, and then subsitute it into mgSin theta, But I don't know how to get the mass?
2. mg sin theta = the component of gravity acting in the direction of motion

You're also right with your introduction of Newton's 2nd Law.

Now equate these 2 and substitute in anything you know and cancel anything you can.
3. Thanks for the help.
4. However... I am now stuck on this question about vectors:

"A particle of mass 500 grams starts from rest at the point A which has position (4i + 2j)m. The resultant force on the particle is (i + 2j)N. Find the position vector of the particle after 3 seconds. "

How do I use F=ma for vectors?
5. In exactly the same way as usual. (you might wanna convert mass to standard units first)

F/m = a

you have a, t, u and you want s

Remember s will have to be worked out using the initial position vector
6. (Original post by Student403)
In exactly the same way as usual. (you might wanna convert mass to standard units first)

F/m = a

you have a, t, u and you want s

Remember s will have to be worked out using the initial position vector
Do I treat i and j components separately still?
7. (Original post by Electrogeek)
Do I treat i and j components separately still?
Yeah keep em separate since you want to work out the position vector. Remember to multiply/divide both i and j components whenever you manipulate expressions
8. (Original post by Student403)
Yeah keep em separate since you want to work out the position vector. Remember to multiply/divide both i and j components whenever you manipulate expressions
Cool. Thanks for the help.

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: January 28, 2016
Today on TSR

### Any tips for freshers...

who are introverts?

### More snow?!

Discussions on TSR

• Latest
Poll

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets

## 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