You are Here: Home >< Maths

# Another M1 vecotr help... watch

1. Q

Rain falling vertically hits the windows of an intercity train which is travelling at 50m/s. A passenger watches the rain streaks on the window and estimates them to be an angle of 20 degrees to the horizontal.

(i) Calculate the speed the rain would run down a stationary window.
(ii) The train starts to slow down with a uniform deceleration and 1.5 minutes later the streaks are at 45 degrees to the horizontal. What is the deceleration of the train??

Could you draw a diagram , becuase it will help me.

Thanks
2. It doesn't look like M1 stuff, it's relative motion isn't it? Which exam board are you in?

Let be the velocity of the train and velocity of the rain respectively.
is vertically downwards, and is horizontal. Please draw a diagram for yourself.

i) So velocity of the rain respects to the train will be which makes an angle of 20 degrees with the horizontal.
-> tan20 = v/u -> v = utan20 (u, v without arrows are speeds)

ii) v = u'tan45 -> u' = v/tan45 = utan20/tan45
t = 1.5 mins = 90s
-> a = (u' - u)/t

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 20, 2005
Today on TSR

### University open days

• Southampton Solent University
Sun, 18 Nov '18
Wed, 21 Nov '18
• Buckinghamshire New University
Wed, 21 Nov '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