Physics Chapter 7
Wrench A is 12 cm long and wrench B is 24 cm long. For a given input force, how does the max torque of wrench A compare to max torque of wrench B?
1/2 as great
What is the centripetal acceleration of a skater moving with a tangential speed of 2.0 m/s in a circular path with radius 2.0 m?
2.0 m/s^2
What expresses Kepler's second law?
A planet sweeps out equal areas of orbit in equal time intervals
What is the correct equation for centripetal acceleration?
Ac=v^2/r
Kepler's laws of planetary motion reconciled
Copernican theory with Tycho Brahe's data
How does the g. force between two objects change if the distance between the objects doubles?
Decreases by a factor of 4
Describe the primary force or forces involved when a car executes a turn. Explain why passengers tend to lean or slide toward the outside of the turn
Friction between the tire and the road is c. force that causes the car to move on a curved path. Passengers lean toward the outside of the turn because their inertia causes them to tend toward moving in a straight line.
What is an expression of g. field strength?
G(me/r^2)
How do planets move?
In circular orbits around the sun
How would the period of an object in a circular orbit change id the radius doubled?
The period would increase by a factor of 2 radical 2
What term describes a force that causes an object to move in a circular path?
centripetal force
What does G stand for?
constant of universal gravitaiton
Tides are caused by
differences in the g. force of the moon at different points on Earth
Evidence confirms that g. mass
equals inertial mass
Where should you push on a door to apply the most torque when opening the door?
far from the hinges of the door
What is c. force that holds planets in orbit?
gravitational force
The force that Earth exerts on the moon
is equal in magnitude to the force the moon exerts on Earth
C. force can be calculated from c. acceleration by
multiplying by the mass
A centripetal force acts
perpendicular to tangential speed but in the same plane
What does efficiency measure?
ratio of work output to work input
What does mechanical advantage measure?
ration of output force to input force
What is the speed of an object in circular motion called?
tangential speed
When a person holds a ball above Earth's surface, the system contains g. potential energy. Where is it stored?
the g. field between the Earth and ball
The speed of an object orbiting another object depends on
the mass of the object being orbited and the distance between the objects
If you were to stand on a bathroom scale in an elevator that is accelerating down, the scale would measure
the normal force between you at the scale
What is a measure of the ability of a force to rotate or accelerate an abject around an axis?
torque
What expresses Kepler's third law?
T^2 & r^3
Explain why an astronaut in orbit experiences apparent weightlessness.
The astronaut is in free fall at the same rate of acceleration as their surroundings.
What is correct?
The closer the force is to the axis of rotation, the less torque is produced.
Explain why an astronaut weighs less on the moon than on Earth.
The g. field strength is less on the moon than the Earth.
Explain why no real machine can have an efficiency of 100%.
The machine would have to be frictionless. Work output is always less than the work input.
What kind of simple machine is like 2 inclined planes placed back-to-back?
Wedge
What is due to inertia?
a ball whirled in a circular motion will move off in a straight line if the string breaks
Centripetal force must involve a change in
an object's velocity
Newton's law of universal g.
can be used to derive Kepler's third law of planetary motion
Using a machine can allow you to
use less force to do a given amount of work
