A student makes a model of the Sun-Earth system by swinging a ball around her head. The student wants to demonstrate what will happen when there is no longer a gravitational attraction between the Sun and the Earth. Using this model, the student lets go of the ball. What path will the ball take?
Newton’s first law, the law of inertia, addresses the behavior of objects in a constant state of motion due to balanced forces acting on them. The law states that an object at rest stays at rest, and an object in motion stays in motion until unbalanced forces act upon it.
Newton's first law describes objects that are either motionless or moving at a constant speed in a straight line.
For things that do travel at constant speed, some force acting on the object exactly balances the forces of friction and air resistance, resulting in a net force of zero.
Inertia refers to an object’s resistance to a change in motion.
Inertia is directly related to mass. The more mass an object has, the more inertia it has, and the more it resists a change in motion.
How does a seatbelt protect you from inertia?
When you are traveling at 55 miles per hour in a car, the brakes that stop your car are not acting on you. Instead, the brakes are acting on the car. That means the car stops, but you continue moving in a straight line until an unbalanced force stops you. That unbalanced force can be a seat belt, an airbag, or a windshield.
When objects are in motion on Earth, it is difficult to see that the object will remain in motion forever unless an unbalanced force acts on the object. This is because the unbalanced force of gravity and friction slow all objects down on Earth.
Objects in space would continue on a straight path if it was not for the gravitational attraction between other objects in space. If the Sun's gravity disappeared one day, the Earth, and all the other planets in our solar system, would continue their path in a straight line instead of continuing their orbits. The video below demonstrates how an object will continue on a straight path in the absence of gravity.
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A student makes a model of the Sun-Earth system by swinging a ball around her head. The student wants to demonstrate what will happen when there is no longer a gravitational attraction between the Sun and the Earth. Using this model, the student lets go of the ball. What path will the ball take?
The direction the ball travels depends on the speed that the student is swinging it.
The ball will continue in its' circular orbit until it falls to the ground.
The ball will fall to the ground immediately after it is released.
The ball will move in a straight line from the point it is released.