Further Mechanics and Thermal Physics (1): Motion in a Circle Flashcards
What unit is used for angles in SHM and circular motion?
radians
An object rotating at a steady speed is said to be in…?
Uniform circular motion
What is the equation for the linear speed of an object in uniform circular motion?
v = 2(pi)r/T
OR
v = 2(pi)rf
where:
2(pi)r - the circumference of the circle
T - the time taken for the object to complete one full rotation
f - frequency of rotation = 1/T
For a cyclist travelling at speed x, what is the speed of the perimeter of each wheel?
x ms^-1
What is the equation for angular displacement per second?
2(pi)/T
where:
T - the time taken for the object to complete oen full rotation
What is the equation for the angular displacement, theta, of an object in time t?
theta = 2(pi)t/T
OR
theta = 2(pi)ft
where:
theta - angular displacement
2(pi)/T - the angular displacement per second
What is the definition of angular displacement?
The radians swept by an object per second
What is the definition of angular speed, omega (lowercase)?
The angular displacement per second
What is the equation for angular speed?
omega = theta/t = 2(pi)t/T/t = 2(pi)/T
OR
2(pi)f
What is the unit of angular speed?
rads^-1
How do you convert from x radians to degrees?
180/(pi) multiplied by x radians = degrees
How do you convert from y degrees to radians?
(pi)/180 multiplied by y degrees = radians
What is the equation for the linear distance, s travelled by a particle in uniform circular motion in time, t?
s = vt = 2(pi)rt/T = (theta)r
theta = angular displacement in time t = 2(pi)t/T
What is the equation for the linear velocity for a particle in circular motion?
v = 2(pi)r/T = (omega)r
omega = angular speed = 2(pi)/T
Describe why objects in circular motion experience a constant force?
- Objects moving in a circular path are constantly changing direction but moving at a constant speed
- therefore, they have a constantly changing velocity and due to Newtons 1st law an object with a changing velocity is acted upon by a resultant force
OR
- therefore, the object is accelerating and due to Newtons 2nd Law, F = ma, an object that is accelerating must be acted on by a resultant force in the direction of the acceleration
What direction does centripetal acceleration act for an object in circular motion?
Towards the centre of the circle
What direction does centripetal force act for an object in circular motion?
Towards the centre of the circle
What is acceleration?
The change in velocity per second/ the rate of change of velocity
What direction does the velocity act for an object in uniform circular motion?
Tangent to the circle
How does the velocity of an object in uniform circular motion change as it moves around the circle?
The change in direction of the velocity is towards the centre of the circle
What is the name for the type of acceleration in uniform circular motion?
Centripetal acceleration
What is the equation for centripetal acceleration (linear speed)?
a = v^2/r
What is the equation for centripetal acceleration (angular speed)?
a = (omega)^2r
What is the name for the type of force in uniform circular motion?
centripetal force
What provides the centripetal force for an object being whirled around on the end of a string?
Tension in the string
What provides the centripetal force for an object in a circular orbit?
The force of gravity between the object and the massive planet
What is the equation for centripetal force of an object moving with uniform circular motion? (linear speed)
F = mv^2/r
as F = ma
What is the equation for centripetal force of an object moving with uniform circular motion? (angular speed)
F = m(omega)^2r
What is the equation for a the centripetal force of a car travelling over the top of a curved hill?
mg - S = mv^2/r
where:
S - The support force from the ground onto the car
mg - The weight of the car
What happens to the support force, S, on a car when th vehicle exceeds a certain speed and loses contact with the road over a curved hill?
S = 0N
What is the maximum v^2/r can equal for a car to remain on the ground when going over a curved hill?
v^2/r < 9.81
What is the centripetal force when a car is going round a roundabout?
The sideways force between the tyres and the road surface
What is the maximum frictional force of a material dependant on?
Its coefficient of friction
If the speed of a car moving around a roundabout is too high, what happens?
The car slips/skids