HELPPPP working with mass and velocity

[desire0701]

This is my first physics class, I am having a lot of trouble doing this homework. Please help.


BELOW ARE 6 BALLS OF DIFFERENT MASS THROWN HORIZONTALLY AT DIFFERENT SPEEDS FROM THE SAME HEIGHT ABOVE THE GROUND. ASSUME THE EFFECTS OF AIR ARE NEGLIGIBLE.

BALL A- 1.0 kg , 30 m/s
BALL B- 0.5 kg, 30 m/s
BALL C- 1.0 kg, 40 m/s
BALL D- 0.3 kg, 60 m/s
BALL E- 1.0 kg, 10 m/s
BALL F- 0.5 kg, 40 m/s

a) rank these baseballs on the basis of the elapsed time before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

b) rank these baseballs on the basis of the horizontal distance traveled before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

 

[PeterO]

This is my first physics class, I am having a lot of trouble doing this homework. Please help.BELOW ARE 6 BALLS OF DIFFERENT MASS THROWN HORIZONTALLY AT DIFFERENT SPEEDS FROM THE SAME HEIGHT ABOVE THE GROUND. ASSUME THE EFFECTS OF AIR ARE NEGLIGIBLE.

BALL A- 1.0 kg , 30 m/s
BALL B- 0.5 kg, 30 m/s
BALL C- 1.0 kg, 40 m/s
BALL D- 0.3 kg, 60 m/s
BALL E- 1.0 kg, 10 m/s
BALL F- 0.5 kg, 40 m/s

a) rank these baseballs on the basis of the elapsed time before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

b) rank these baseballs on the basis of the horizontal distance traveled before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

To get an idea of how A and B [or C and F] compare you could try putting two objects of different mass beside each other on a table, then using a ruler, push them both off withe the same speed and see what happens, both from the point of view of time and distance.

Don't use marshmellows or ping-pong balls as air resistance might have an effect.

 

[desire0701]

thank you. Although I am still very confused on what formula to use in order to answer these 2 questions :/

 

[fluidistic]

This is my first physics class, I am having a lot of trouble doing this homework. Please help.


BELOW ARE 6 BALLS OF DIFFERENT MASS THROWN HORIZONTALLY AT DIFFERENT SPEEDS FROM THE SAME HEIGHT ABOVE THE GROUND. ASSUME THE EFFECTS OF AIR ARE NEGLIGIBLE.

BALL A- 1.0 kg , 30 m/s
BALL B- 0.5 kg, 30 m/s
BALL C- 1.0 kg, 40 m/s
BALL D- 0.3 kg, 60 m/s
BALL E- 1.0 kg, 10 m/s
BALL F- 0.5 kg, 40 m/s

a) rank these baseballs on the basis of the elapsed time before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

b) rank these baseballs on the basis of the horizontal distance traveled before they hit the ground.
Largest 1._____ 2._____3._____4._____5._____6_____ Smallest

What does your intuition tells you here?

 

[PeterO]

thank you. Although I am still very confused on what formula to use in order to answer these 2 questions :/

I am suggesting pushing things off a table so that you might use Physics rather than a formula to get the answer.

 

[desire0701]

for part a I believe that since they all have the same heights they will all fall at the same time. I am not quite sure

for part b I am unsure about what formula to use or how to use it I am completely confused :/

 

[PeterO]

thank you. Although I am still very confused on what formula to use in order to answer these 2 questions :/

Note: you could try flicking two masses of the edge if the table at different speed - but at the same time. Quite difficult to manage, but you could try.

 

[desire0701]

thanks you :)

 

[desire0701]

both objects having different masses fell at the same time. Therefore part A would b unable to rank considering they all have the same heightand mass does not affect, only gravity. Thank you once again.

Do you know how I can solve part B?

 

[PeterO]

both objects having different masses fell at the same time. Therefore part A would b unable to rank considering they all have the same heightand mass does not affect, only gravity. Thank you once again.

Do you know how I can solve part B?

Judging the time is easy, as you will have heard the impacts with the floor at the same time.

To get an idea for different speeds, you could try flicking a mass off at different speeds, but concentrate on the sound.
You will hear two clicks - one when the ruler hits the mass and a second when the mass hits the floor.

If you lined up a series of coins on the edge of a table and worked you way through them, you would hear each pair of clicks while the time interval from the previous one is fresh in your mind.

 

[fluidistic]

for part a I believe that since they all have the same heights they will all fall at the same time. I am not quite sure

for part b I am unsure about what formula to use or how to use it I am completely confused :/

If you believe that for part a) they should all hit the ground at the same time, you believe the time they take to fall is independent of the mass and on the horizontal velocity of the balls.
Let's suppose for the sake of it, that they all take 1 s to fall and hit the ground. What will be the horizontal distance that each traveled?

Edit: To check out if you are right that they all take the same time to fall, you can do PeterO's experiment.

 

[desire0701]

for part b they require me to show my work in formula... I began working with d=Votf + at^2 but it doesn't seem to be giving me the right answer

 

[fluidistic]

for part b they require me to show my work in formula... I began working with d=Votf + at^2 but it doesn't seem to be giving me the right answer

Before to run blindly into any formula, check out our help.

 

[desire0701]

I did PeterO's experiment by dropping a pencil and a heavy pencil case from the same height and at the same time and realized they both hit the ground at the same time despite the difference in mass. Now i am unsure about part b.

 

[fluidistic]

I did PeterO's experiment by dropping a pencil and a heavy pencil case from the same height and at the same time and realized they both hit the ground at the same time despite the difference in mass. Now i am unsure about part b.

Ok perfect!
For part b, my tip was "Let's suppose for the sake of it, that they all take 1 s to fall and hit the ground. What will be the horizontal distance that each traveled?"
If you go at 30 m/s and you're stopped after 1 s, what is the distance you traveled?

 

[desire0701]

d=Votf + 1/2at^2
d=1/2(10)(1)^2
d=5m

would this be correct?

 

[fluidistic]

d=Votf + 1/2at^2
d=1/2(10)(1)^2
d=5m

would this be correct?

I'm afraid, no.
I'm asking a question that does not require the use of this kind of formula.
An equivalent question could be "you're in a car traveling at a constant speed of 100 km/h. After one hour, what is the distance you've travelled"?

 

[desire0701]

if my car is traveling 100km/h in 1 hour i would have traveled 100km

 

[desire0701]

therefore both balls A & B would have traveled 30 m in 1 sec. Balls C & F traveled 40 m in 1 sec. Ball D 60 m in 1 sec and Ball E 10m in 1 sec

 

[fluidistic]

therefore both balls A & B would have traveled 30 m in 1 sec. Balls C & F traveled 40 m in 1 sec. Ball D 60 m in 1 sec and Ball E 10m in 1 sec

You got it.
I'll help you a bit more and tell you that if you change the 1 s by any number of second, call it "j", balls A & B would travel 30 jm within the j seconds, etc.
So now you know the actual ranking for part b).
If you need to work with formula's, I'd start to calculate the time it takes for all the balls to touch the ground if they're released by an arbitrary height "h".
P.S.:Any other helper is welcome, I must go to sleep soon...

 

[desire0701]

Thank you so much!

 

[desire0701]

Im sorry to keep bothering you but once I've found the time it takes for all the balls to hit the ground. what formula should I use that includes an arbitrary height?

 

[PeterO]

d=Votf + 1/2at^2
d=1/2(10)(1)^2
d=5m

would this be correct?

Have a read of this

http://equalrightsforall.net/online_tutorial/classical_mechanics/Rectilinear_Motion/Kinematical_Equations/007_Projectile_Motion_in_Two.htm