Exta Class Ppt

8/11/2019 Exta Class Ppt

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1 D


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2 C

Distance moved parallel to the direction of force


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3 A


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4 C

At 2.6s, h = 0.6m

Displacement = 1.30.6

=0.70m


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5 D

In x-t graph, gradient = velocity


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6 A

Graph starting from zero

Straight lines, parallel to each other


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7 C

Up thrust > Weight


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8 B

300 N

10,200-9800


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9 C

E = F l / A x

x 1 /E

xs / xb =Eb/ Es= Eb/ 2 Eb= 0.50


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10 C

F = k x

x = 0.13 0.040

k = F / x


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11

(a) Weight of the water = m g

= v d g

= 5 x 10-3

x 0.010 x 1000 x 9.81

= Weight = 0.49 (N)


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(b) weight (of cork) = weight of displaced water

= 0.49 or 0.5 N

weight (of cork) = upthrust


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12

(a)(i)Hard

resistant to indentation/scratching Or

surface is resistant to plastic deformation


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(ii)Stiff

high Youngs ModulusOr

large force / load / stress for (small) extension /

strain / deformationOr

(large) force / load / stress for small extension /

strain / deformation

(not resistant to, hard to bend)


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(iii)High tensile strength

withstand/bear/undergo a large stress/force

(under tension) before breaking/fracture


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(b) (Large stretching) force/stress/tension

appliedOr wire is being stretched/taut

Will not plastically /permanently deform Or will

return to original length(when forceremoved)

Idea that thepitch/frequency/tone/tune/sound/note willalter.


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14

a(i)

Energy = power time

Energy = 4.2 W 0.4 s

Energy = 1.68 (J)


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(ii)

Ek= mv2

V = 6.5 ms-1/ 5.9 ms-1


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(iii)

Energy is dissipated to heat

Or work is done against friction

Or not all the energy becomes kinetic energy

Or air resistance on car

Or friction between car/wheels/pin and track

Or resistance in motor


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(b)

No resultant force is acting on the car

(Car) continues moving: in a straight line

Or in same direction Or with same velocity.


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15

(a)As the temperature increases, the viscosity

decreases

at a decreasing rateOr

the rate of decrease is greater at lower

temperatures Or exponentially


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(b)(i)

F = 6 r v

= F /6 r v

= N / m m s-1

= N m-2s = Pa s


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(ii) 6 r v = weight of the sphere = m g

= 1.12 x 10-3 Pa s ( from the graph)

V = m g / 6 r

= 3.7 ms-1


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16

(a)Consider the half motion

v = u + at

0 = 2.8 + (-9.81) tt = 0. 285 s

Total time = 0.285 x 2

= 0.57 s


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(b) Horizontal = Horizontal velocity x time

distance

= 8 x 0.6

= 4.8 m


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(c)At the time of landing,

u = 2.8 ms-1, a = 9.81 ms-2, s = 0.50 m

v 2= u2+ 2 a s

v = 4.2 ms-1

v = u + att = 4.22.8 / 9.81 = 0.14 s

Distance = v x t = 8 x 0.14

=1.1m


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17

(a)(i)Use of E= m g h

= 810 9.81 6.0

= 47, 700 (J)


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(ii) (useful) energy = 40total energy

transferred transferred

= 40 / 100 x 47,000

= 19 100 J

Resistive force , F = E /d = 19,100/0.20

= 9.6 x 104N


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(b)(i) Stress = Force / Area

Strain = Extension / Original lengthYoung modulus,E = F l /A x

= 2

x (compression) = F l / A E= 0.0083 (m)


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(ii)

Energy stored, E = F x

= x7 x 10 5 x .01

= 3.5 x 10 3 J


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(iii) 1.

Graph:

Permanent/plastic compression/deformation

Or does not return to its original length/shape

Effect:

Becomes too thin

Or will not compress

Or no longer elastic

Or becomes brittle


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2.

More work done in loading than unloading the

wood

Or more energy is absorbed/stored than released

Or the area between the lines shows energy is

dissipatedOr the area while applying the force > the areawhile releasing

Or (the area in) the hysteresis loop shows energyis dissipated


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18

9(a)


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(b)(i)

L cos 20 = mg

L = 0.66N

L sin20

L

cos

20

mg

20


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(ii)

L sin 20 = ma

a = 0.66 x sin 20 / 0.063

a = 3.58 m s-2

Exta Class Ppt

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