time down ramp #1=2 sec.,time across table top is 5sec.,time up ramp #2 is 4 sec., distance across table top between ramp is 20 meter long

To find the speed or velocity of an object, we can use the formula:

Speed = Distance / Time

Given the information provided:
- Time down ramp #1 = 2 seconds
- Time across tabletop = 5 seconds
- Time up ramp #2 = 4 seconds
- Distance across tabletop between ramps = 20 meters

First, let's find the speed down the ramp:
Speed down ramp = Distance down ramp / Time down ramp #1

Since we don't have the distance down the ramp, we can't calculate the speed down the ramp.

Next, let's find the speed across the tabletop:
Speed across tabletop = Distance across tabletop / Time across tabletop
Speed across tabletop = 20 meters / 5 seconds
Speed across tabletop = 4 meters per second

Finally, let's find the speed up ramp #2:
Speed up ramp #2 = Distance up ramp #2 / Time up ramp #2

Since we don't have the distance up ramp #2, we can't calculate the speed up ramp #2.

Therefore, we can only calculate the speed across the tabletop, which is 4 meters per second.