Which optical devices can form only virtual images?

Jessie ran 5000 meters from the cops and an average speed of 6 meters / second before he got caught . how long did he run?

The volume of a gas is halved during an adiabatic compression that increases the pressure by a factor of 2.5. what is the specific heat ratio? show the math steps .

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?