True or False: A projectile always lands with the same velocity it had at launch.
False. If the launch and landing height are different, the velocity will also be different.
What formula is used to calculate the time for an object to fall to the ground from rest?
t=SQRT(2s/a)
At what angle is flight time of a projectile maximised?
90 degrees (vertical)
At what angle is horizontal range of a projectile maximised?
45 degrees
How does the velocity of a projectile change over the course of its flight over level ground?
Horizontal velocity is constant.
Vertical velocity reduces at a constant rate until it reaches 0m/s at the peak height, then continues to reduce until it lands with a negative velocity the same magnitude as the initial velocity.
What formula relates centripetal force and instantaneous velocity?
F=(mv^2)/r
What unit is used to measure angular velocity
radians per second
What variables affect the torque on a rotating object?
The force applied
The distance of the force from the axis
The angle that the force is applied at
What is the difference between mass and weight?
Mass is the amount of matter
Weight is how much force gravity exerts on an object
Weight = mass x gravity
What is the equation for centripetal acceleration?
a=(v^2)/r
What provides the centripal force for a satellite?
Gravity
State Newton’s Law of Universal Gravitation
F=(GMm)/r^2
Define escape velocity
The minimum velocity required to escape the gravitational field of a body.
v=SQRT(2GM/r)
What is Kepler’s Third Law?
The square of the orbital period is proportional to the cube of the orbital radius.
What is the total mechanical energy of a satellite?
the sum of gravitational potential energy and kinetic energy
U+K= -GMm/2r
Why are astronauts “weightless” in orbit?
They are in continuous free fall, experiencing apparent weightlessness. Centripetal force comes from gravity and so they technically still have weight.
What is Kepler’s Second Law?
The imaginary line between a star and a planet sweeps out equal areas in equal amounts of time.
What is Kepler’s First Law?
The path of a planet around a star is an elipse with the star as one of the two foci.
What are the conditions for geostationary orbit?
Orbit above equator, period = 24 hrs, same direction as Earth’s rotation.
Compare low Earth orbit (LEO) and geostationary orbit.
LEO: low altitude, short period. GEO: high altitude, 24-hour period.
What is the work done by gravity on an orbiting satellite?
No work is done on as energy states do not change (unless accounting for atmospheric drag).
