Projectiles Help (1 Viewer)

[Roors]

Hey!
I have an experimental assessment for Physics, where i have to study the motion of a projectile launched by a mechanical device & it has to be reliable.
I have to be able to experimentally find the max height, range, timeof flight & initial velocity.
I'm not sure what to do- i am soooo confused!!
Does anyone have any ideas for me? maybe somehting i can use or construct!
Your ideas would be GREAT!!!
THANKS!

 

[...]

so u gonna build one of those caterpilla things and shoot rocks out of them to measure stuff?????

 

[Roors]

well...im not sure what ur talking about....but i do need to build somehting, something thats not too hard to build...but i'm wondering if maybe u could give me an idea, and maybe a method......??

 

[Dangar]

We did this experiment at school. We used a toy trolley cart at a fixed angle, but that a slingshot would be a good idea, just with a rubber band or however you make them, glue to a wedge of wood at a 45 degree angle and then mark a line or point that you pull it back to each time before firing so it has the same initial velocity. Then we put carbon sheets down, so when the ball landed we could measure the range.

So using v=s/t you can get the initial x velocity, then with u(x)=ucos45 you can get the initial velocity and etc. calculating evrything.

I don't know if it counts as a mechaninal device tho

 

[jims]

that sounds too much like design n tech...
i remember we did something a lot simpler. we rolled a small ball down a ramp and along a table then into a cup on the floor. by calculating the distance it travelled along the table (after the ramp) and the time taken we found its speed. we knew the table hieght. so then we just calc where we should put the cup.

 

[PoLaRbEaR]

i remember we did something a lot simpler. we rolled a small ball down a ramp and along a table then into a cup on the floor. by calculating the distance it travelled along the table (after the ramp) and the time taken we found its speed. we knew the table hieght. so then we just calc where we should put the cup.

Yeh that's an easier method...i did that one at skool as well....but he did say 'mechanical device' so im not too sure if this experiment would be appropriate..

 

[Roors]

Tanks for ur replies ppl!
He did say "mechanical device" so im assuming it should consist of springs. Someone suggested to me an egg launcher, but i would have NO idea how to build one!

 

[...]

u play Warcraft or Age of Empire or any of those games???

well...make urself a small platform and get a decent size wooden spoon...get a very strong spring(and i mean a decent one) and make it so that when u release a trigger, the wooden spoon will flung out...

u know back in the ancient war times how ppl make these vehicle that release huge bulk of rock to knock down walls?? make a mini version of that

 

[PoLaRbEaR]

hehe yeh a catapult...they also used to light them up so it'll crash down in flames...like in the beginning of the movie Gladiator..
I dont think paper would be a good medium to use as ur projectile cuz it seems to me as tho it'll fly too high or too far...maybe use something heavy and cover it in paint so you know exactly where it lands and then use the formulas and work out wat you want...and if you do decide to do the catapult experiment then also take into consideration the height above ground the projectile is being released at...

 

[...]

but one problem i just thought was that i think the experiment needs to also include something with the projectile angle...

 

[PoLaRbEaR]

You can use a protractor [not the ones you buy but the big wooden ones that the teachers usually have] to measure the angle between the platform and the direction of projection...i can't think of any accurate measurement tools tho...

 

[inasero]

what we ppl at sbhs did was to roll a marble off a bench and photograph the trajectory using a video camera set to 25 fps (frames per second). This was in conjunction with a crudely devised graph of 5 cm spacings used as a backdrop...thus knowing the position and velocity of the projectile at any given time in a two dimensional plane (although heisenberg probably wouldnt agree lol) we could analyse the two vector components of force (horizontal and vertical) to demonstate that they were independent (insofar as the experimental results suggested)...

edit: this is only an analysis of half motion so you should ideally conduct other experiments for a full survey of projectile motion..

 

[pigs_can_fly]

just build a ramp with a slight turn at the end so instead of fallng straight down, the marble will be launched upwards slightly. the ramps should look sort of like a slanted J, if u know what i mean. then you can analyse full flight motion

 

[inasero]

souds good! care to divulge more info?

 

[pigs_can_fly]

i think we did this last year
basically there are like prebuilt ramps on a cardboard back with a grid. roll a marble down, film it with a camera, play it back and analyse its motion

 

[haz_it_all]

we did this exp in yr 11.....wat they want ya to do is jus get to bits of wood and set it up like this |__ and jus use one of those peg guns with the ruler and peg stuck to it ( like the old skool days in yr 3 ) and set it up to be 45 degrees, and calculate wat max ht + max range will be and test the apparatus to see if it accurate... from the range u will be able to calculate velocity and acceleration due to gravity...sorry if this doesnt make sence

 

[Roors]

sounds cool..but ummm wats a peg gun?
like i've sorta created something....im not sure how good my idea is though...

 

[haz_it_all]

well wat u do is u get like a 30cm ruler and get a peg (from the clothesline ) and stickytape it down onto the ruler, wat u do next is stickytape a rubber band down to one end of the ruler and u pull the rubber band into the peg, so the peg holds the rubber band....to fire all u do is press the peg....the problem with this is its inaccuarte because u have to take into consideration the projectile itself. and since there is continously changing tension in the rubber band the projectile will be launced at different velocities. it depends on whether this is jus to demonstrate ur understandin of projectiles or if this is an assesment