Allow to mount/unmount a specific device to a specific user
you could create a simple file:
sudo visudo -f /etc/sudoers.d/myOverrides
with this directive:
User ALL = NOPASSWD:/sbin/mount -t ntfs /dev/sda2 /home/User/mnt/ntfs
This allow User to runs mount command with those parameter without entering a password.
Here is sudo manual for more details.