What Happens Next?
Two identical balls are released simultaneously from the same height, but one is launched horizontally while the other is simply dropped; neglecting air resistance, which lands first?
They land simultaneously because their initial vertical velocities and vertical accelerations are identical.
“A satellite remains in orbit because there is no gravity in space.”
Gravity supplies the centripetal force that continuously accelerates the satellite towards Earth.
Why can a person pull a tablecloth quickly from beneath dishes without moving the dishes very far?
The dishes’ inertia resists a rapid change in motion while friction acts for only a short time.
Name the two bridges that cross the central sections of Lake Burley Griffin.
Commonwealth Avenue Bridge and Kings Avenue Bridge
What colour of visible light has the highest photon energy?
Violet light has the highest photon energy because it has the highest visible frequency.
A charged particle enters a uniform magnetic field moving exactly parallel to the field; what happens to its motion?
It continues undeflected because the magnetic force is zero when its velocity is parallel to the field.
“A step-up transformer creates extra electrical energy because its output voltage is greater.”
Its output current is correspondingly smaller, so an ideal transformer’s output power equals its input power.
Why can birds safely perch on a single high-voltage power line?
Both feet are at nearly the same electric potential, so little current passes through the bird.
Streets in nearly every Canberra suburb follow a naming theme; what is the theme of the streets in Phillip?
Phillip’s streets are named in connection with the First, Second and Third Fleets
Why can no one hear an explosion occurring in the vacuum of space?
Sound is a mechanical wave and requires particles through which to propagate.
An astronaut inside an orbiting spacecraft releases a ball from rest beside them; what happens to the ball?
It remains beside the astronaut because both are in free fall with the same orbital acceleration.
“Increasing the intensity of light must allow it to eject electrons from any metal.”
Electrons are ejected only if individual photons exceed the metal’s work function, regardless of total intensity.
A metal bench feels colder than a wooden bench at the same temperature; why?
Metal conducts thermal energy away from the body faster than wood does.
Which Canberra suburb has streets named after Australian geological resources, including Nickel Street?
Beard has streets named after Australian geological resources.
A spacecraft uses solar panels twice as far from the Sun as Earth; compared with Earth, what fraction of the solar intensity does it receive?
It receives one-quarter of the intensity because intensity follows an inverse-square relationship.
Identical lamps A and B are connected in series to an ideal battery, and a wire is then connected directly across lamp B; what happens to each lamp?
Lamp B goes out while lamp A becomes brighter because the wire bypasses B and reduces the circuit’s total resistance.
“A person standing at the centre of a hollow spherical planet would be crushed by gravity pulling inward from every direction.”
The gravitational forces from the surrounding shell cancel, producing zero net gravitational field at the centre.
Why does increasing a photoelectric light source’s intensity increase the number of emitted electrons but not their maximum kinetic energy?
Greater intensity supplies more photons, while each photon’s energy and therefore the maximum electron energy depend on frequency.
From what lookout can you see the Anzac Parade line up with Parliament house?
Mount Ainslie
Why is the daytime sky blue but the setting Sun often red?
The atmosphere scatters shorter wavelengths more strongly, leaving proportionally more red light after sunlight travels through a longer atmospheric path.
Alice travels rapidly to a star and returns while Bob remains on Earth; each sees the other’s moving clock run slowly during constant-speed travel, so why can Alice still be younger when they reunite?
Alice changes inertial frames during the journey while Bob does not, so their situations are not symmetrical.
“Length contraction means fast-moving objects are physically compressed by a force.”
Length contraction is a difference between measurements made in different reference frames, not deformation caused by a force.
Why can high-speed muons created in the upper atmosphere reach Earth’s surface even though their rest-frame lifetimes appear too short?
Earth observers measure their lifetimes as dilated, while the muons measure the atmosphere’s thickness as length-contracted.
What was the name of the astrophysicist who was the former Vice Chancellor at ANU?
Brain P Schmidt.
What was the first type of object from which gravitational waves were directly detected?
The waves came from the merger of two black holes, first directly detected in 2015.