Physics Hsc - Space (Entire Unit Summary)
HSC PHYSICS: SPACE
* 1. “The Earth has a gravitational field that exerts a force on objects both on and around it.” Students learn to “define weight as the force on an object due to a gravitational field.” Mass is the amount of matter in a body whereas weight is the force due to gravity acting on a mass. Mass will not change where the acceleration due to gravity is different but the weight will change.
For example, bathroom weights are calibrated in kg, but actually measure weight as they work by the mass on them compressing the spring. Therefore, it takes into account Earth’s gravitational pull. On the Moon, the gravitational force is about 1/6 that of Earth, so the spring will compress about 1/6 as much. The scales will therefor read 1.6kg instead of 10kg.
W = mg where W = weight, m = mass, g = acceleration due to gravity. Astronauts in space appear weightless even though gravity is acting on them. At the height of a typical space station gravity is about a third of its value on Earth. The astronauts appear weightless because they are falling around the Earth with the same acceleration as their space station. You could get the same situation on Earth if you were in a lift when the cable broke. True weight is equal to mg for whatever value g has at that location. Apparent weight is equal to the reaction force exerted on the object and is equal to mg + ma where ‘a’ is the upward acceleration of the object. (For an object accelerating down, a is negative) Students learn to “explain that a change in gravitational potential energy is related to work done.” When an object is lifted in a gravitational field the work done is equal to the increase in gravitational potential energy. If an object falls then the gravitational field does work on the object. The amount of work done by the gravitational field is equal to the amount of work required to restore the object to its original position.
Consider the
* 1. “The Earth has a gravitational field that exerts a force on objects both on and around it.” Students learn to “define weight as the force on an object due to a gravitational field.” Mass is the amount of matter in a body whereas weight is the force due to gravity acting on a mass. Mass will not change where the acceleration due to gravity is different but the weight will change.
For example, bathroom weights are calibrated in kg, but actually measure weight as they work by the mass on them compressing the spring. Therefore, it takes into account Earth’s gravitational pull. On the Moon, the gravitational force is about 1/6 that of Earth, so the spring will compress about 1/6 as much. The scales will therefor read 1.6kg instead of 10kg.
W = mg where W = weight, m = mass, g = acceleration due to gravity. Astronauts in space appear weightless even though gravity is acting on them. At the height of a typical space station gravity is about a third of its value on Earth. The astronauts appear weightless because they are falling around the Earth with the same acceleration as their space station. You could get the same situation on Earth if you were in a lift when the cable broke. True weight is equal to mg for whatever value g has at that location. Apparent weight is equal to the reaction force exerted on the object and is equal to mg + ma where ‘a’ is the upward acceleration of the object. (For an object accelerating down, a is negative) Students learn to “explain that a change in gravitational potential energy is related to work done.” When an object is lifted in a gravitational field the work done is equal to the increase in gravitational potential energy. If an object falls then the gravitational field does work on the object. The amount of work done by the gravitational field is equal to the amount of work required to restore the object to its original position.
Consider the