Chapter 8 Flashcards
(13 cards)
When can a torque only exist?
When there is a force present
A force doesn’t always mean torque tho
Where would the best place be to exert a the most torque on a door for example?
The furthest point from the hinge perpendicular to the door
What are the signs that go with the directions of torque?
Positive- counterclockwise
Negative- clockwise
What is the lever arm?
What is it’s equation with torque?
The perpendicular distance from the axis of rotation to a line drawn along the direction of force
d=rSinθ
τ=Fd = FrSinθ
What is the centre of gravity?
What does uniform mean?
The point where the total force of gravity is acting on an object
When a question says uniform it means the centre of gravity if the geometric centre of the object
What does it mean to be in mechanical equilibrium?
No linear or angular acceleration
Net torque and net force must equal 0
ΣF= transnational equilibrium
Στ= rotational equilibrium
Look through problems on oct 29
Okay
What is the relationship between torque and angular acceleration?
ΣF=ma Ft=mat Ft(r)=mat(r) Ft(r)=m(rα)r τ=(mr^2)α τ=Iα
mr^2=moment of Inertia
What is inertia?
Quantity which is constant for a small object located a fixed distance from axis of rotation
It depends on the total mass and how the mass is distributed
Slide 9 oct 31
How is conservation of energy used for rotational kinetic energy?
If Wnc=0 then,
(KEt+KEr+PE)i=(KEt+KEr+PE)f
How is the linear speed of an axle related to the angular speed of the wheel when an object is rolling without slipping?
Vaxle=2πr/T=2π/T (r)= ωr
KEtotal=KErot+KEtrans
1/2Iω^2+1/2Mv^2
ω=v/R and v=Rω
If a disk and a hoop are both released from a slope and have same mass and radius what will hit bottom first?
Disk will hit bottom first since it has lower moment of inertia
Lower moment of inertia=increase angular spin
How can torque be found using angular momentum?
Στ=ΔL/Δt
L= angular momentum
