Definition of Gravity

When we see gravity at work, we generally only notice it acting on a single object (i.e. the apple falling from the tree or the car rolling down the hill). In fact, gravity is a force that pulls two objects together. The strength of the attraction between the two objects depends on:

• The mass of the objects
• The distance between the objects

Mass refers to how much matter an object is comprised of. The mass of an object is determined by how much space it takes up (its volume) and how tightly packs its matter is (its density). Heavier objects generally have greater mass, and vice versa.

The shorter the distance between the two objects or the greater the mass, the stronger the force of gravity pulling them toward each other will be. Gravity acts on every object in the universe to some extent. Between any two objects, the force of gravity is present. For the most part, this force is not noticeable. Gravity is working right now, between you and the computer in front of you.

The only gravitational force we are aware of in our day-to-day lives is the force pulling us and the objects around us toward the center of the Earth. This is because the Earth is the only nearby object with a great enough mass to exert a noticeable gravitational pull.

Your Vehicle’s Center of Gravity

Gravity does not always act on an object as you would expect. Rather than moving directly toward the Earth’s center, an object may turn as it falls, or tip over from a standing position. This is caused by the object’s center of gravity, which describes the point around which the object’s weight is evenly balanced. If you throw an object into the air, it will only fall directly back toward the earth without changing position if its center of gravity is in its exact center, as would be the case with an evenly weighted ball. 

Your vehicle’s center of gravity will determine how it is pulled toward the Earth in different situations. Cars with a higher center of gravity are more likely to flip, turn over or roll during a collision. SUVs are particularly susceptible to this, as the body of the car sits further from the ground. Racing cars and other vehicles which are designed for fast maneuvering typically have a very low center of gravity and can take corners at speed without tipping over, as they are built to sit close to the tarmac.

Gravity When Driving on Hills

Gravity affects your speed of travel when going uphill and downhill because of the change in gravitational pull as you move towards, or away from, the center of the earth.

When you are driving uphill, the force of gravity is working against you to slow you down. You may need to accelerate or change to a lower gear to maintain your speed. This is important especially when you are overtaking a vehicle on an uphill climb.

When you drive downhill, the reverse is true. Gravity causes you to go faster and increases your stopping distance. You may need to shift to a lower gear or smoothly apply your brakes to reach a safe speed and control your vehicle.

Automobiles are equipped with safety equipment such as brakes and gear to counteract the effect of gravity. Low gears are used to overcome gravity when you drive downhill or uphill.

Gravity When Parking on Hills

When you leave a vehicle parked on an incline, gravity works to pull your vehicle downhill. You should ensure that your vehicle is parked in such a way that it would not roll down the hill.

KEEPING YOUR VEHICLE FROM ROLLING DOWNHILL
To keep your vehicle from rolling away, you should leave your vehicle in a low gear or in “Park” if it has an automatic transmission. You should always engage your parking brake and may even need to block your wheels by placing an object in front of or behind the tires.

JUST IN CASE YOUR PARKING BRAKE FAILS
Just in case your parking brake fails, you should always turn the front wheels of your vehicle so that it would not roll into the traffic lane. The way you should turn your wheels depends on whether you are parked facing uphill or downhill and whether or not there is a curb.

WHEN YOUR VEHICLE IS PARKED FACING DOWNHILL
When you are parking facing downhill, you should always turn your front wheels towards the curb or side of the road. The curb or side of the road would act as a barrier, preventing your vehicle from moving from its parked position.

WHEN YOUR VEHICLE IS PARKED FACING UPHILL AND THERE IS A CURB
When  your vehicle is parked facing uphill, and there is a curb, you should  always turn your front wheels towards the middle of the road and allow the vehicle to roll back against the curb. If you are parking facing uphill and there is no curb, you should turn your wheels toward the side of the road.