# Why can't the acceleration of a wedge be found by simply...

AStudentNeedsHelp
mentor note: thread moved to h/w forum so template is missing

Hi, I have recently been learning relative acceleration and I have a bit of trouble with basics;

In a problem with a smooth wedge on a smooth plane, a mass is gently placed on the wedge and I've been asked to find the acceleration of the wedge.
Seemed pretty straightforward, just apply F=ma for the wedge?
NO
The answer was obtained by applying F=ma for the particle parallel to the wedge and for the whole system horizontally.
Why couldn't I get the answer by just applying F=ma for the wedge?

NascentOxygen
Staff Emeritus
Does the question ask for the relative horizontal acceleration? The wedge moves one way, and the body moves the other way.

SammyS
Staff Emeritus
Homework Helper
Gold Member
mentor note: thread moved to h/w forum so template is missing

Hi, I have recently been learning relative acceleration and I have a bit of trouble with basics;

In a problem with a smooth wedge on a smooth plane, a mass is gently placed on the wedge and I've been asked to find the acceleration of the wedge.
Seemed pretty straightforward, just apply F=ma for the wedge?
NO
The answer was obtained by applying F=ma for the particle parallel to the wedge and for the whole system horizontally.
Why couldn't I get the answer by just applying F=ma for the wedge?
How do you propose finding the net force acting on the wedge ?

You should probably use the homework template as per the guidelines. I'm not sure you've given enough information about the problem for anyone to be able to help you.