Can employer force salaried employees to work over 40 hours?

Are you an exempt or non-exempt employee?  If you are exempt employee, there is no upper limit on how many hours you could be asked to work.  However, just because you are salaried doesn't mean that you are necessarily "exempt" from certain labor laws.  Being paid on a salary basis is part of the test for most forms of exemption, but it's not the only element; it is possible to be salaried and to get overtime.  Basically, exempt employees are: Management (ieyou supervise other people and have have considerable discretion in your work); Professionals (your job requires advanced or technical training - engineers, accountants, lawyers, etc); Administrators (if you they exercise considerable discretion in your position). If not, then you are a non-exempt employee and work time is paid time and for any hours that you work over 40 per week, it has to be paid as overtime. 

Note:  At this point you should go to the your state's or the Department of Labor's website and check to see whether or not you are an "exempt" or "non-exempt" employee.