The acceleration due to gravity is 9.81 m/s^2. As you increase the angle that you’re driving on, the more gravity begins to pull you back, not just down. You’ll have to forgive my skills as an artist, but I tried to draw a diagram to explain what happens.
In the first diagram, the car is on a level slope. So when gravity pulls on
the car, it pulls straight down and doesn’t slow down the car from moving
forward.
When we start going up a hill, now gravity isn’t pulling straight down on our car any more (at least not from the car’s point of view). The arrows I drew represent how gravity is affecting your car. Gravity always pulls straight down toward the earth, but to the car, part of that gravity pulls it down toward the road, and part pulls it backwards.
As you increase the angle more and more, gravity pulls the car backwards more and more. You can imagine if we tried to drive straight up a wall, gravity would act completely to pull the car backwards, and nothing would be holding it to the wall.
Now, figuring out the formula for this is a trigonometry problem. I’m not going to explain the geometry, but it works out to this:
Acceleration toward road = g * cos A Acceleration backward = g * sin A
Where g = 9.81 m/s^s, and A is the angle. In your example, if we were using 170 degrees (which I assume you actually mean 10 degrees: 180 – 170 = 10). We would get 9.81 m/s^2 * cos (10) = 9.81 * .174 = 1.70 m/s^2. So your car’s acceleration will be reduced by 1.70 m/s^2.