Question

Why does a car appear lighter than its weight when travelling at a high speed?

Answer 1

"high" to what... High can be speed of light or 200 m/s

Answer 2

Because the air up the car runs much faster than the air beneath the car,and as a result,the car can get a force which can offset the gravity.

Answer 3

It depends. When the car is accelerating, you have to look at the resultant net vector force acting on it. Gravity is always acting downward, while the wheels are going to be accelerating it forward. Add the two together, and you'll find that the resultant force will not be completely in the downward direction, thus the normal force acting on it will be less. It will essentially "weigh less". But... if it's traveling at constant speed, none of this applies. See above post.