Flashcards in Chapter 1 - Analysing Motion Deck (24):
What is a Projectile?
It is any object that is thrown or projected into the air and is moving freely. (It has no power source)
If air resistance is ignored, what are the only forces acting on a projectile?
If air resistance is ignored, the only force acting on a projectile during its flight is it's attraction to the Earth due to gravity.
Gravity - constant, directed vertically downwards causing the projectile to continually deviate from a straight line path to follow a parabolic path.
Does the horizontal component change when gravity is acted upon a projectile?
No, a projectile movies with uniform velocity since there are no forces acting in this direction.
Why would a taller athlete have an advantage in the shot-put?
They launch the shot from a greater heigh and a will achieve a greater distance. Recent female world champions have been around 2.0m tall.
Is the sum of the gravitational potential energy and kinetic energy the same at all points?
Yes, because at the lowest point in its flight, gravitational potential energy is a minimum and kinetic energy is maximum. And vice versa for the highest point.
Why ballet dancers seem to float in the air?
They raise their arms and legs which allows them to raise the position of their centre of mass so that it is higher in the torso. The effect of this is that the dancer's head follows a lower and flatter line.
What is a Period?
It is the time taken to move once around the circle.
Average Speed of an object moving in a circular path is:
v = 2 pie r / T
v = distance/ time period
Define Frequency (f).
The number of revolutions (or rotations) completed in one second. (Hz) or (rpm).
Define Speed (v).
This refers to the linear speed of a point moving in a circular path. Often just called the velocity.
Define Rotational Speed.
This, like frequency is simply the number of rotations/ revolutions per second. Sometimes also called angular speed. (Hz) or (rpm).
What is the Universal Gravitational Law?
Between any 2 physical objects there is an attraction force directly proportional with their masses. And indirectly/ inversely proportional with the square of the distance between their centers.
Is the velocity of an object kept constant when it is moving in a circular path?
No, it is changing.
How does the velocity of an object moving in a circular path constantly changing?
It is accelerating even thought its speed is not changing. (Direction)
What does Centripetal Acceleration mean?
'Centre-seeking'. Acceleration towards the centre; however, even though the hammer is accelerating towards the centre of the circle, it never gets any closer to the centre.
Ac = v^2 / r
Why does the kinetic energy of a body that is moving horizontally with uniform circular motion remain constant even though an unbalanced force is continually acting on it?
Because the force is always perpendicular to the motion of the body.
What is a Conical Pendulum?
It is an object that can move in a circular path attached to a stein for a cable that is not horizontal. Here, the centre of the circular path is not the end of the string, but in the same horizontal plane as the object itself.
What does the vertical component of the tension do? (Conical Pendulum)
It balances the force due to gravity on the object.
What is the acceleration of an object in a conical pendulum?
It is horizontal and towards the centre of the circular path.,
What does banking a track do?
It eliminates the need for sideways frictional force to turn. When the speed and angle are such that there is no sideways frictional force, the speed is known as the Design speed.
What are the forces acting on a vehicle traveling at the design speed on a banked track?
Gravity and the normal force from the track.
What do objects that are moving in vertical circular paths experience?
They experience a centripetal acceleration and centripetal force that acts towards the centre of their path.
What is the centripetal acceleration during a circular motion in a Vertical plane?
It will equal to that due to gravity.