Kinematics/Mechanics

Question 1

the big 5 equations

Answer 1

1) d = vit + 1/2at^2
2) d = vft - 1/2at^2
3) vf^2 = Vi^2 + 2ad
4) vf = vi + at
5) d = 1/2 (vf+vi) t

Question 2

equations for projectile motion (horizontal)

Answer 2

displacement: d=v•t
velocity: vf=vi (constant), vx=vcosθ
acceleration: a=0

Question 3

equations for projectile motion (vertical)

Answer 3

displacement: d=vit + 1/2 at^2 (in y plane)
velocity: vf = vi + (at) (in y plane), vy=vsinθ
acceleration: a= -g

Question 4

Newton’s first law

Answer 4

If an object is at rest or moving with a constant velocity, the object will remain doing so unless acted upon by a net force.
no Fnet = no a

Question 5

Newton’s second law (Fnet)

Answer 5

Fnet = ma

Question 6

Newton’s third law

Answer 6

F1on2 = -F2on1

- for action reaction pairs to be valid, they cannot be acting on the same object (ie can’t be Fnormal and Fg)

Question 7

weight

Answer 7

w=mg

Question 8

Newton’s law of gravitation

Answer 8

Fgrav = G Mm/r^2

Question 9

formula for gravity (on any given planet)

Answer 9

g = GM/r^2

Question 10

Kinetic friction

Answer 10

Fk = μk•Fn

- note Fn is magnitude, not vector

Question 11

Static friction

Answer 11

Maximum value Fs = μs•Fn

- always greater than Fk

Question 12

force of gravity acting parallel/perpendicular to an inclined plane

Answer 12

parallel: Fg = mgsinθ
perpendicular: Fg = mgcosθ

Question 13

μs for inclined plane

Answer 13

μs ≥ tanθ

Question 14

how to find Ft for pulley systems

Answer 14

Ft = mg/(#of strings-1)

Question 15

centre of mass formula

Answer 15

xcm = m1•x1 + m2•x2 … / m1 + m2 …

- must chose a reference point for x

Question 16

centre of gravity formula

Answer 16

xCG = w1•x1 + w2•x2 … / w1 + w2 …

- must chose a reference point for x

Question 17

centripetal acceleration formula

Answer 17

ac = v^2/r

Question 18

centripetal force formula

Answer 18

Fc = m•ac = m•v^2/r

Question 19

torque (2 formulae)

Answer 19

1) τ = rFsinθ (if at 90º, just rF)

2) τ = Fl (l=lever arm, extend force back then make 90º line from pivot)

Question 20

translational vs rotational equilibrium vs static equilibrium

Answer 20

translational: Fnet = 0
rotational: τnet = 0
static: Fnet, τnet, and v = 0

Question 21

rotational inertia properties

Answer 21

If mass is closer to rotational exit, i is smaller and therefore easier to rotate (and vice versa).

Question 22

work (3)

Answer 22

W = F•dcosθ
W = P/t
W = ΔEk
scalar (can be -/+ but no direction!)

Question 23

power (2)

Answer 23

P = W/t
P = F•v

Question 24

Kinetic Energy

Answer 24

Ek = 1/2mv^2

Question 25

Potential Energy (2)

Answer 25

ΔEp = mgh (+ or -)
ΔEp = -W(by gravity)
- note: gravity is a conservative force

Question 26

Total mechanical energy/conservation of energy/conservation of energy with outside forces

Answer 26

E = Ek + Ep
Ei = Ef
Ei + W(byF) = Ef
- all E’s are scalar

Question 27

percent efficiency

Answer 27

% = W(output)/Energy(input)

Question 28

mechanical advantage

Answer 28

MA = effort distance/resistance distance

- resistance distance being the distance of it moving without the machine

Question 29

momentum

Answer 29

p = mv

Question 30

conduction vs convection vs radiation

Answer 30

conduction: atoms in direct contact, transferring energy.
convection: energy transfer via moving fluid (including air).
radiation: energy carried by light waves then absorbed.

Question 31

impulse

Answer 31

J = Δp = Δ(mv) = FΔt

Question 32

conservation of momentum

Answer 32

Δp system = 0

pi = pf (m1v1 = m2v2)

Question 33

elastic vs inelastic vs perfectly inelastic collisions

Answer 33

elastic: total p and Ek conserved
inelastic: total p conserved
perfectly inelastic: objects stick together after

Question 34

angular momentum

Answer 34

L =ιmv = Iω
ι = lever arm
ω = angular velocity
angular momentum is conserved (Iωi = Iωf)