Question

A rock is thrown straight down with an initial velocity of 15 m/s from the Verrazano Narrows Bridge in New York City. The roadway of this bridge is 70 m above water. Take upwards to be the positive direction.

1. Calculate the displacement at a time of 1.0 s.

2. Calculate the velocity at a time of 1.0 s.

Answer 1

The attempt at a solution: -5.6

Answer 2

how did you get that? I have like 4 more problems just like this so I kinda wanna know how to get the answer

Answer 3

I've figured out the displacement by (10.5)(1)+(1/2)(9.8)(1.0)^2=-15.4 I don't know how to find velocity though.

Answer 4

wait! calculate the velocity at t = 1.0 s.

Answer 5

this is actually physics and math at the same time!!

Answer 6

do you know calculus?

Answer 7

yes I aced it why

Answer 8

You have the distance formula \(x = x_0+V_0t +(1/2) gt^2\)
if you choose upward is + direction, then, the formula becomes
\[X(t) = X_0-V_0t-(1/2) gt^2\]

Answer 9

the -15.4 wasn't right

Answer 10

Now, At the beginning, \(X_0=70,V_0= 15m/s, g=9.8\) , and at t = 1.0 s, just plug in to get the answer for a

Answer 11

Since I was of no help, I am leaving.
<<<<<<<<<<<

Answer 12

For velocity, if you know calculus, just take derivative of X w.r.t.t
If you don't know calculus, this is the formula for velocity at time t
\[V(t) = V_0+gt\]
Minus sign to show that it is down ward.

Answer 13

I got 50.095 for the displacement, is that right?

Answer 14

Well according to this source, no. But neither am I and this guy isn't a calculus professor..

Answer 15

However, these other 2 sources say yes you r correct

Answer 16

@brainzonly haha i'm so confused

Answer 17

I only have 1 more try at this problem, if I tell you the answer do you think you could help me figure out how they got it?

Answer 18

yes ill try

Answer 19

try 50.095 first

Answer 20

I did, it was wrong

Answer 21

:(

Answer 22

any other ideas? before I guess a number haha

Answer 23

nope. sorry....
@mathmale help!

Answer 24

@Loser66 @brainzonly the answer for the displacement was -19.9, do you know how they got that?

Answer 25

give me a minute

Answer 26

I don't know. but check this out:
http://phys.libretexts.org/TextMaps/Map%3A_College_Physics_(OpenStax)/02._Kinematics/2.8_Falling_Objects

Answer 27

\(x=x_0-V_0t-(1/2)gt^2\)
replace all, you have
\(x = 70 - 15*1-(1/2)9.8*(1)^2= 50.1\)
but the question is about the displacement. That is this.