|   | 1 |  initial version  | 
Here is how to do it.
Works with the following version of Sage.
sage: version()
'SageMath version 9.0, Release Date: 2020-01-01'
Declare variable t and function v,
and define function F in terms of those: 
sage: t = SR.var('t')
sage: v = function('v')
sage: F(t) = v(t)*t^2
Derivative of the function:
sage: F.diff(t)
t |--> t^2*diff(v(t), t) + 2*t*v(t)
Derivative of the expression:
sage: F(t).diff(t)
t^2*diff(v(t), t) + 2*t*v(t)
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.