Hide Ribbon control in SharePoint 2010
The Security Trimmer control can be place around the ribbon in Master page.The Permission String attribute value can be changed based on the requirement.
Replace the code in master page and paste the below code in master page.
<SharePoint:SPSecurityTrimmedControl PermissionsString="ManagePermissions" runat="server">
<div id="s4-ribbonrow" class="s4-pr s4-ribbonrowhidetitle">
</div>
</SharePoint:SPSecurityTrimmedControl>