ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: fELiX on November 14, 2007, 01:10:59 pm

1) A ball is thrown vertically upwards and returns to the throwers hand. During its flight, the speed of the ball is: constant/increasing/decreasing/increasing and decreasing (circle one)
2) An archer fires an arrow vertically into the air from groung level at a speed of 12m/s.
a)Find initial vertical acceleration of arrow
b)For how long will the arrow be in the air
c)What is the acceleration of the arrow at the top of its flight
d)What maximum height does the arrow reach
e)What is the speed of the arrow just before it impacts with the ground
f)Describe any forces acting on the arrow during its flight and any variations in these forces.
Please help. I just want to pass year 11 physics
Thank You
Cheers

1. It's decreasing when it travels up, increasing when it goes down
2. a) We live in a world without air resistance, so acceleration is always 9.8m/s^2 or 10. Generally, in physics we say it's 10 because it's an easier number, but go with whatever your teacher tells you to use.
b) There is more than one way to do this question. I am going to find the time it takes to reach the top of its 'flight', and then double it (seeing as it takes the same time to go up and come down)
So a=10, u=12, v=0, t=?
v=u+at
0=12  10t
10t = 12
t=1.2s to reach top => total flight = 2.4s
c) acceleration is constant > 10m/s^2
d) a=10, u=12, v=0 (because top of flight), y=? (you can use your 't' value from before, but it is a good idea not to in case you made a mistake)
v^2 = u^22ay
144 = 20y
y = 144/20 m = 7.2 I think
e) Flight is symmetrical (from ground level to ground level) > hits at same speed it leaves at > 12m/s
f)This depends if the question is with or without air resistance (you never do calculations with air resistance because it is too hard)
Without air resistance, the only force is acceleration downwards, which is constant.
With air resistance, there is also a force in the opposite direction to the direction it's traveling in, which is larger when it is going faster (so at the top there is no air resistance force)

1) A ball is thrown vertically upwards and returns to the throwers hand. During its flight, the speed of the ball is: constant/increasing/decreasing/increasing and decreasing (circle one)
2) An archer fires an arrow vertically into the air from groung level at a speed of 12m/s.
a)Find initial vertical acceleration of arrow
b)For how long will the arrow be in the air
c)What is the acceleration of the arrow at the top of its flight
d)What maximum height does the arrow reach
e)What is the speed of the arrow just before it impacts with the ground
f)Describe any forces acting on the arrow during its flight and any variations in these forces.
Please help. I just want to pass year 11 physics
Thank You
Cheers
What is meant by initial vertical acceleration?
I think it might be either 10m/s/s or maybe 0(Just taking a punt)

vertical accelleration is always gravity. in physics we take it as 10m/s^2... in maths you use 9.8

i ignored general maths advanced this yr especially the kinematics section because i did 3/4 phsyics, but i took 10 as acceleration all the way trhough the exam! it was annoying, why must maths complicate everything :P!

i ignored general maths advanced this yr especially the kinematics section because i did 3/4 phsyics, but i took 10 as acceleration all the way trhough the exam! it was annoying, why must maths complicate everything :P!
I think it's more a matter of VCE Physics simplifying everything.