Topic 6: Circular Motion and Gravitism Flashcards
How can an object be moving at a constant speed and also accelerating in a circular path?
Its direction of motion is constantly changing therefore its velocity is constantly changing. As acceleration is the rate of change of velocity the object is accelerating.
Define angular velocity.
The angular displacement divided by the time taken. Must remember formula as not given. w =2πf. The units are rad s-1.
Give the formula for finding angular velocity from the period.
Rearrange T = 1/f for the frequency. Then use the following formula: w = 2πf
How is speed calculated in banked corners?
v = √rgtanθ
What is the horizontal and vertical components of the normal reaction force in banked corners?
Horizontal component provides the centripetal force.
Frsinθ
Vertical component is weight (mg).
Frcosθ
How can the minimum speed needed to move in vertical circular motion be calculated?
At the minimum speed, the reaction force at the top of the loop = 0 and Fc (centripetal force) = Fg (weight force).
V = √rg
*Minimum speed does not depend on the mass of the object.
What does the weight we feel in vertical circular motion depend on?
The weight we feels depends on the size of the reaction force not the size of the weight force.
At the top of the loop the reaction force = 0 so we feel weightless. At the bottom of the loop the reaction force is greater than the weight force so we feel heavier.
What are the main differences between horizontal circular motion and vertical circular motion?
In vertical circular motion the size of the normal reaction force acting on the object varies throughout the motion and the speed of the object may not be constant as the energy changes between Ek and Ep.
Define Newton’s universal law of gravitation.
Every single point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of their separation.
Define gravitational field.
A region of space where a charged object experiences a force due to its charge.
Define gravitational field strength.
The force per unit mass experienced by a small positive test mass placed in the field. Measured in Nkg-1. (g)
How to find the speed for an orbiting object?
v = √GM/r
*The speed required to maintain an orbit depends on the radius of the orbit but not the mass of the satellite.
How do you find speed in circular motion?
v = 2πr/T
What is the centripetal force acting in orbital motion?
The centripetal force is provided by the gravitational force on the satellite.
What is the relationship between the radius of a circular orbit and its period?
T²∝R³
