How could you determine the instantaneous speed during a

trip?

Look at your speedometer for say, a couple of seconds. Depends on whether or not you are moving on average at a constant speed (speedo won't change much) or whether you're in a polluting traffic jam/queue in which case the speedo will go up and down like a yo yo. to determine the speed, you'd probably need to plot the speed on the speedo against the times at which the speedo speeds were read from the speedo.

The moving object has both velocity and speed it shows how fast an object is moved instantaneous speed is the motion rate of an object at particular time period of a moment