AQA AS Physics Unit 2 (PHYA2) June 9th 2016 Resit paper

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Reply 120

GdotMdot

Original post by Exams987

isn't the formula S=0.5(v+u)t

U was 0 in the question as it was from rest

Reply 121

ryandaniels2015

How has everyone prepared for this? If u do the 10 past papers, how much of the paper will be stuff never seen before on past papers?

Reply 122

boyyo

In a projectile, if air resisitance is taken into account, will that effect both the horizontal and vertical distance travelled by object? I feel like the vertical distance is not effected, can anyone clarify?

Reply 123

TSRPAV

Original post by boyyo

Only horizontal

Reply 124

philo-jitsu

Original post by boyyo

Distance wont be affected in projectile questions as it hits the floor...but air resistance does affect downwards force just as much as horizontal force. SO actually air resitance would both increase and decrease the length travelled horizontally, as the time taken to hit the floor would be longer, but its horizontal speed would decline faster......this is why they dont really include air resitance

Reply 125

Exams987

Original post by GdotMdot

U was 0 in the question as it was from rest

in the question was the motion linear ?

if the motion is linear then i think you use s=vt

Reply 126

TSRPAV

Original post by TSRPAV

Only horizontal

e.g throw a ball horizontally from 1m off the ground when the wind is against you, it will be displaced 1m vertically from you when its on the ground,however horizontally it will be displaced dependant on how strong the wind is e.g xm

throw a ball in a vacuum container horizontally from 1m off the ground it will still be displaced 1m vertically from you when on the ground but will be displaced further horizontally at something like 3xm

Reply 127

boyyo

Original post by philo-jitsu

I kind off get what your saying, but say q2 here:
https://5505b400f275fd9f29b9b4679ca512236789cf2e.googledrive.com/host/0B1ZiqBksUHNYZEhDNnU3TUxGaG8/January%202010%20QP%20-%20Unit%202%20AQA%20Physics.pdf

Part c asks why it wouldnt travel that far, and it mentions how you said the horizontal speed declines etc. So the air resistance causes the horizontal spped to fall and therefore the distance reached to be less?

Reply 128

ryandaniels2015

any ideas?

Original post by ryandaniels2015

How has everyone prepared for this? If u do the 10 past papers, how much of the paper will be stuff never seen before on past papers?

Reply 129

GdotMdot

Original post by Exams987

in the question was the motion linear ?

if the motion is linear then i think you use s=vt

Oh i see, acceleration would be constant as it is for vertical.

Reply 130

ryandaniels2015

For this question why don't you use the displacement 3 to calculate time taken?

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Reply 131

philo-jitsu

Original post by ryandaniels2015

For this question why don't you use the displacement 3 to calculate time taken?

The question says 'speed' of 6.7ms....which is a magnitude not a vector, direction doesnt come into it.

Reply 132

ryandaniels2015

Original post by philo-jitsu

The question says 'speed' of 6.7ms....which is a magnitude not a vector, direction doesnt come into it.

But the bike has travelled upwards 6.7m/s so wouldn't u consider vertical height?

Reply 133

philo-jitsu

Original post by boyyo

Yep, the friction acts directly against the motion vector.....so its horizontal and vertical really....but for these questions just say air resistance produces a force against the motion of the object, which decreases the velocity resulting in less distance travelled....which is pretty much what you said I am just realizing lol

Reply 134

philo-jitsu

Original post by ryandaniels2015

But the bike has travelled upwards 6.7m/s so wouldn't u consider vertical height?

Vector includes direction...speed doesnt,

Reply 135

TSRPAV

Original post by boyyo

kinda, basically if you resolve horizontally in this "theory" without air resistance there is no resistive forces to decelerate(slow it down) and it will not be accelerating as there is no thrust proving acceleration(no overall force as no acceleration so only v=s/t applies)so we use the impulse velocity, which is what it is travelling as it left the racket and as the time of horizontal and vertical displacement is the same/constant (read about monkey-hunter model) we can use v=s/t so v is proportional to s (as t is constant).so basically all values are max

When air resistance occurs in practice horizontally: the time to displace horizontally and vertically is still the same(constant) however there is a resistive drag force on the ball which causes it to decelerate, as there is no thrust on the ball after it has left the racket the only horizontal force acting on it is the air resistance which will be large and slowly decrease(decelerate the ball) until zero when it no longer moves horizontally So as the ball is decelerating its mean velocity is less. so v=s/t (where t is constant) if v decreases, t is constant then s must decrease