Correcting Wrong Answers Flashcards
Get them right. All of them. (5 cards)
In a cycling race, each member of a team takes turns cycling at the front. The others cycle in a line as close behind each other as possible. Using your knowledge of physics, explain why the team of riders cycle in this way.
Cyclists use slipstream to reduce the effect of air resistance/drag on them.
* If less air resistance acts on them, they can accelerate more.
* Cyclists take turns being lead cyclist to conserve energy.
* Cyclists are crouched down (streamlined shape) to reduce air resistance.
* Air passes easily over each cyclist until it reaches the end of the line, where there will be
turbulence created. It would be harder to cycle in this ‘dirty air’ (would use more energy).
In practice, the acceleration of a plane is not constant. Explain why the acceleration decreases.
As the speed of the plane increases, the frictional force (air resistance) acting in the opposite direction to its motion also increases.
This means that the unbalanced force acting on the plane will change, altering the acceleration.
A package falls vertically from a helicopter. After some time the package reaches its terminal velocity.
A group of students make the following statements about the package when it reaches its
terminal velocity.
I The weight of the package is less than the air resistance acting on the package.
II The forces acting on the package are balanced.
III The package is accelerating towards the ground at
9·8 ms−2
Which of these statements is/are correct?
I is wrong because then the package wouldn’t be travelling downwards.
II is right.
III is wrong because terminal velocity is where air resistance matches gravity, so the object won’t be accelerating since the forces are equal.
A group of students make the following statements about the satellite.
I The greater the altitude of a satellite the shorter its orbital period.
II The satellite has a constant vertical acceleration.
III As the satellite orbits the planet, its vertical velocity increases.
Which of these statements is/are correct?
I is wrong.
II is right because all objects accelerate towards Earth’s centre at 9.8ms-2.
III is wrong because the velocity is not vertical, it is a constant motion that curves around the Earth. Horizontal motion is constant. The vertical velocity measured from one point of the earth would be increasing but as it passes it, the velocity would reset since its no longer travelling towards that point.
What measurements need to be made to calculate the acceleration of a trolley down a ramp?
Length/width of card
Time taken for card to pass through the light gate
Time taken for trolley to travel from starting position to light gate
