Would you be doing more work going up the stairs twice as fast?

If an athlete runs once around a track, back to the starting line, her average velocity is zero. true or false?

What explosion in the upper solar atmosphere releases about as much energy as millions of 100-megaton hydrogen bombs exploding simultaneously?

Amoving freight car collides with an identical one that is at rest. if momentum is conserved, what happens to the second car after the collision? it attains the same speed as the first car. it moves at half the speed of the first car. it moves at twice the speed of the first car.