Question

Gina is driving her car to work, but she’s stopped at a red light. When the light turns green, she presses the gas pedal and accelerates (speeds up) to move the car. Which of these statements is true the moment Gina presses the gas pedal? Assume the road is flat and level. A. The net force on the car is zero in the horizontal direction. B. The net force on the car is zero in the horizontal and the vertical directions. C. The net force on the car is greater than zero in the horizontal direction. D. The net force on the car is greater than zero in the vertical direction. E. The net force on the car is less than zero in the vertical direction.

Answer 1

Since car is initially at rest so at that position the net force on car in vertical as well as horizontal both direction is zero

but after lights are green the car will speed up in horizontal direction

so now we can say that

It will accelerate in horizontal direction

So now as per Newton's formula we have

$F = ma$

so now the force in horizontal direction will become nonzero while in vertical direction car is still in equilibrium

So now we can say

$F_x = ma$

$F_y = 0$

so the correct answer will be

C. The net force on the car is greater than zero in the horizontal direction.