1997 hsc from Success one (1 Viewer)

[gamecw]

check out the projectile motion question.. the last part doesnt quite make sense... it says that the plane is travelling at A CONSTANT velocity, then it drops this object and blah (read it urself)

then the answer from the back of book assumes that the object has a initial horizontal velocity the same as the horizontal velocity of the plane.

but wudnt the object fall vertically (no horizontal motion) if it is droped from the plane(since the plane is traveling at a constant velocity).. (or am i wrong?)

but i dont think its required to know in max1 course.. so how wud u do the question?

 

[B35tY]

ignoring wind resistance, if you drop something out your car window, does it stop (which from your point of view would be like going backwards really quickly) or go at the same speed as you? Same thing. When the object is dropped, it will have the same horizontal velocity as the plane itself.

In real life this wouldn't really work, but you know.

 

[Riviet]

Try this:

Get someone in your house to run in front of you and get them to drop an object out of their hand. While this is happening, position your eyes so they are in line with their hand and watch the trajectory of the object.

 

[gamecw]

u cant really try anythin to prove this coz u cant keep ur velocity constant..

just tell me in terms of physics.. am i right or the book..

i thought since the speed is constant, it is an intertial frame of reference, so droping an item will fall vertically?

lol i think im wrong

 

[ianc]

ah the joys of physics

just because it is dropped from a plane doesnt mean the object suddenly loses its horizontal velocity.

btw in ur profile it says u do physics - this is the same question galileo pondered all those years ago when thinking about relativity and trying to prove a heliocentric solar system

anyway good luck with the exam tomorrow everyone!

edit: relative to someone in the plane, the canister will fall vertically. However the plane is also moving, with the same horizontal velocity as the canister.

From the sailor's point of view, the canister makes a parabolic arc as it falls from the plane

the 3unit maths stuff always operates from the frame of reference on the ground - using displacement in terms of time

 

[gamecw]

ic then im definately wrong.. anyways good luck to uz too!

im getin around around 75/84 from past hsc papers under timelimit, once 100% and once 82/84. but i still make a lot of silly mistakes, usually 5 marks worth

 

[Riviet]

u cant really try anythin to prove this coz u cant keep ur velocity constant..

just tell me in terms of physics.. am i right or the book..

i thought since the speed is constant, it is an intertial frame of reference, so droping an item will fall vertically?

lol i think im wrong

Well if you think about it in terms of momentum, the object will continue to possess that horizontal component while also start falling since it's been dropped out of the plane. However, air resistance does eventually reduce the horizontal component till it's zero and then the object just falls freely under gravity.