Mechanics

Question 1

Scalars?

Answer 1

Qualities with Magnitude

Question 2

Vectors?

Answer 2

Qualities with Magnitude and direction

Question 3

Speed

Answer 3

rate of change of distance v = d/t (ms-1)

Question 4

Velocity

Answer 4

rate of change of displacement v = displacement/s

Question 5

Instantaneous speed

Answer 5

rate of change of distance at one particular tim\

Question 6

Average speed

Answer 6

the speed over a period of time

Question 7

Acceleration

Answer 7

rate of change of velocity a = ∆v/t (ms-2)
- Whether acceleration is +ve or -ve depends on the direction
- not if its speeding up or down

Question 8

v = u + at

Answer 8

v = final velocity (ms-1)
u = initial velocity (ms-1)
a = acceleration (ms-2)
t = time (s)

Question 9

v^2 = u^2 + 2as

Answer 9

v = final velocity (ms-1)
u = initial velocity (ms-1)
a = acceleration (ms-2)
s = displacement (m)

Question 10

s = ut + 1/2at^2

Answer 10

t = time (s)
u = initial velocity (ms-1)
a = acceleration (ms-2)
s = displacement (m)

Question 11

s = (v+u)t/2

Answer 11

t = time (s)
u = initial velocity (ms-1)
v = final velocity (ms-1)
s = displacement (m)

Question 12

Range

Answer 12

How far it travelled horizontally
Range = Horizontal velocity x time of flight

Question 13

Mass (m)

Answer 13

amount of matter in an object (kg) (does not ∆ if an object ∆ its position

Question 14

Weight (W)

Answer 14

force of gravity acting on an object (N) (it will ∆ if an object ∆ its position)

Question 15

W = mg

Answer 15

W = Weight (N)
m = Mass (kg)
g = gravity (9.81 Nkg-1 on earth)

Question 16

Newton’s first law

Answer 16

“an object continues in uniform motion in a straight line or at rest unless a resultant external force acts”

Question 17

Newton’s second law

Answer 17

“the resultant force on an object is proportional to the acceleration providing the mass of the object remains constant”
- bigger force -> bigger acceleration
- F = ma

Question 18

Newton’s third law

Answer 18

“for every action on one object there is an equal but opposite reaction on another object”

Question 19

F = ma

Answer 19

F = Force (N)
m = mass (kg)
a = acceleration (ms-2)

Question 20

Ff ≤ μsR

Answer 20

Ff = static friction force (N)
μs = coefficient of static friction (max value = 1)
R = normal reaction force (N)
Static Friction = “about to move”

Question 21

Ff = μdR

Answer 21

Ff = dynamic friction force (N)
μd = coefficient of dynamic friction (max value = 1)
R = normal reaction force (N)
Dynamic friction = sliding friction (not affected by speed) μd < μs

Question 22

Ek = 1/2 mv^2

Answer 22

Ek = kinetic energy (J)
m = mass (kg)
v = speed (ms-1)

Question 23

∆Ep = mg∆h

Answer 23

∆Ep = Gravitational potential energy (J)
m = mass (kg)
g = gravity
∆h = change in height

Question 24

Ep = 1/2 k∆x^2

Answer 24

Ep = Elastic potential energy (J)
k = spring constant (Nm-1)
∆x = extension or compression (m) (change in length)
F (applied force (N)) = ∆x

Question 25

W = Fs

Answer 25

W = work (J)
F = force (N)
s = displacement (m)

Question 26

W = F s cosθ

Answer 26

W = work (J) (transfer of energy)
F = force (N)
s = displacement (m)
θ = angle between F & S

Question 27

Force required to lift an object =?

Answer 27

Objects weight

Question 28

P = Fv

Answer 28

P = power (W)(Js-1)
F = force (N) (constant)
v = velocity (ms-1) (constant)

Question 29

Efficiency =

Answer 29

useful work out/total work in = useful power out/total power in

Question 30

p = mv

Answer 30

p = linear momentum (kgms-1)(Ns)
m = mass (kg)
v = velocity (ms-1)

Question 31

Conservation of momentum definition?

Answer 31

“the total linear momentum of a system remains constant provided no resultant external force acts (e.g. friction)”.
total p-before = total p-after

Question 32

Elastic collision =

Answer 32

no kinetic energy is lost during the collision

Question 33

inelastic collison =

Answer 33

kinetic energy is lost

Question 34

Ek = p^2/2m

Answer 34

Ek = kinetic energy (J)
p = momentum (kgms-1)(Ns)
m = mass (kg)

Question 35

Impulse =?

Answer 35

Change in momentum (F∆t = ∆p)

Question 36

F = ∆p/∆t

Answer 36

F = Force (N)
∆p = change in momentum (impulse) (kgms-1)(Ns)
∆t = change in time

Question 37

Explosions

Answer 37

Kinetic energy will always increase in an explosion
p=mv
big m = little v
little m = big v

Question 38

projectile?

Answer 38

An object moving through air under the influence of only one force, gravity