Projectile and relative motion help

[Torpedo007]

Homework Statement

A boy is standing on a long railroad car throws a ball straight upwards.The car is moving on a horizontal road with an accelaration of 1m/s^2. and the projection velocity is 9.8m/s.How far behind the boy will the ball fall on the car.

Homework Equations

Not entirely sure what to use but i tried using the basic equations of motions and relative velocity but without an actual velocity for the rail car i found it really hard

The Attempt at a Solution

I fist used the basic V=U+at and found the time taken to go up.

Hence time taken to come down will be 2t.In this same the car should have traveled a certain distance.Now this is where I am stuck since i only have the acceleration not the speed of the car D:

I juggled around but couldn't get the proper answer which was 2 meters

Any help would be much appreciated!

 

[tiny-tim]

Welcome to PF!

Hi Torpedo007! Welcome to PF!

(try using the X² icon just above the Reply box )

Show us what you've tried, and where you're stuck, and then we'll know how to help!

 

[Torpedo007]

Hi Torpedo007! Welcome to PF!

(try using the X² icon just above the Reply box )

Show us what you've tried, and where you're stuck, and then we'll know how to help!

Hey thanks for the reply ;D

I fist used the basic V=U+at and found the time taken to go up.

Hence time taken to come down will be 2t.In this same the car should have traveled a certain distance.Now this is where I am stuck since i only have the acceleration not the speed of the car D:

 

[tiny-tim]

Hey Torpedo007!

I fist used the basic V=U+at and found the time taken to go up.

Hence time taken to come down will be 2t.

(btw, you could have used V = -U and found the total time, or 0 = Ut + at²/2 )

In this same the car should have traveled a certain distance.Now this is where I am stuck since i only have the acceleration not the speed of the car D:

Call the speed of the car c, put it in the x equation, and you should find it cancels at the end.

 

[Torpedo007]

Call the speed of the car c, put it in the x equation, and you should find it cancels at the end.

Sorry to be a bother but can you just elaborate a bit more please , i don't understand D:

 

[tiny-tim]

The boy has initial speed c₀, and acceleration 1.

The ball has initial distance x = 0 and initial horizontal speed v_x,0 = c₀.

So when the ball lands, where is the ball, and where is the boy?

 

[Torpedo007]

The boy has initial speed c₀, and acceleration 1.

The ball has initial distance x = 0 and initial horizontal speed v_x,0 = c₀.

So when the ball lands, where is the ball, and where is the boy?

Ah i think i finally i got it ;D thanks a load