Question

At t=0sec a ball, initially at rest, starts to roll down a ramp with constant acceleration. You notice it moves 1ft between t=0sec and t=1sec. How far does it move between t=1 and t=2sec?

Answer 1

xo=vo*t-(.5)at^2 (a common kinematic equation)

Answer 2

xo=displacement
vo=initial velocity (in your case zero)
t=time
a=acceleration which you want to find.

Answer 3

Ok, so my acceleration is -2ft/sec^2

Answer 4

@cherio12

Answer 5

positive, xo would be negative in this case because it is going down

Answer 6

but yet, 2m/s^2

Answer 7

yes*

Answer 8

ok so now I plug the acceleration back into the initial equation to find displacement?

Answer 9

yes, .5*2*(2^2)=x-1

Answer 10

I'm just not entirely clear why the acceleration is positive and the displacement is negative

Answer 11

there are the same sign

Answer 12

in the equation i wrote -.5*a*t^2

Answer 13

if they are the same sign the result be a negative final displacement

Answer 14

it is the common formula, but it depends on the direction the acceleration is acting. If it acts the same way the object goes its positive

Answer 15

like...you could argue that the acceleration of the ball is DOWN the hill. and the ball roles DOWN the hill

Answer 16

Hmm...I used a positive displacement and negative acceleration

Answer 17

kinda confused

Answer 18

well, so why do you believe the acceleration is negative?

Answer 19

because it is downward acceleration

Answer 20

okay i would agree. so now why do you believe displacement is positive?

Answer 21

because it is traveling a positive distance away from a starting point

Answer 22

on a horizontal axis