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What is a standard candle?

A standard candle is an astronomical object that has a known absolute magnitude (intrinsic brightness). They are extremely important to astronomers since by measuring the apparent magnitude of the object the...
AS
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Calculate the length of a 120m (as measured by the astronaut) spaceship travelling at 0.85c as measured by a stationary observer

The length of the spaceship of 120m was measured at rest relative to the spaceship so we will take that as the proper length, dennoted L proper We first calculate the Lorentz factor: Ɣ = 1/sqrt(1-(v/c) 2 ) Ɣ...
KM
Answered by Kerr M. • Physics tutor
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A student is measuring the acceleration due to gravity, g. They drop a piece of card from rest, from a vertical height of 0.75m above a light gate. The light gate measures the card's speed as it passes to be 3.84 m/s. Calculate an estimate for g.

This question is simply a matter of finding and applying the correct equation of motion. First, draw a diagram - even if the situation in the questions seems really simple, it's always useful to draw a diagr...
PM
Answered by Philippa M. • Physics tutor
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A supertanker of mass 4.0 × 10^8 kg, cruising at an initial speed of 4.5 m s^(–1), takes one hour to come to rest. Assume the force slowing down the tanker is constant.

From newton's first law, an object remains in its inertial frame until a force acts upon it. This means that according to a stationary observer, the object will remain at rest or continue moving at the same ...
JC
Answered by Jack C. • Physics tutor
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How do I resolve forces on a slope?

For any question which asks you to consider multiple forces acting on a body, the first thing you should do is draw a clear diagram, with all forces (and in this case angles) labelled.Once this has been done...
DB
Answered by Dan B. • Physics tutor
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