The force of gravity pulling down on the barbell is 756 newtons (N) How many
newtons of force are exerted by the
weightlifter to hold the barbell up?

Explanation:

The same. The force down (the weight of the barbells) is counter balanced by the weight up ( a person holding the barbells). A little later on, you are going to draw force diagrams showing that these two forces are drawn acting in opposite directions.

You can satisfy yourself by drawing a box and putting 1 arrow pointing up on the bottom and labeling it 756 up and another arrow on the top of the box pointing down and labeling it 756. They balance.

for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

hope this : )