* Gravity and Mass: The strength of gravitational force is directly proportional to mass. This means the more massive an object is, the stronger its gravitational pull.

* Comparing the Objects:

* A bowling ball is significantly heavier than a sand grain, marble, or tennis ball.

* While the difference in gravitational force between a tennis ball and a marble is small, it's still greater than the force exerted by a sand grain.

Important Note: While the bowling ball has the most gravitational force of the objects listed, the actual force is still very small. We don't notice the gravitational pull of these objects because the Earth's gravity is so much stronger.