A basic a, v, t problem?

  • #1
SoConfused__
23
0

Homework Statement


If Carol Ann wakes up and crawls across her bedroom at an aceeleration of 0.45 m/s^2 forward for 1.3s, how fast would she be going after 1.3 seconds if he had started with a velocity of 0.25 m/s forward?

Homework Equations


d = (v1+v2/2)t
a = v2 - v1 /t


The Attempt at a Solution


so we're looking for V right? Which would be v1 & v2.
v2 - v1 = at
= 0.25 x 1.3
= 0.325

but the answer here says 0.84 m/s forward.

What am I doing wrong? Please help, thank you so much.
 

Answers and Replies

  • #2
willem2
2,089
348
The equation you use is right. How you apply it, is not. I don't understand at all what you meant with" we're looking for V right? Which would be v1 & v2.
v1 is the initial velocity, wich is 0.25 m/s
v2 is the final velocity, wich is what were after.
you haven't used the acceleration at all.
 
  • #3
SoConfused__
23
0
But what we're looking for is "how fast would she be going after the 1.3 s" isn't that the speed?
 
  • #4
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,143
165

Homework Statement


If Carol Ann wakes up and crawls across her bedroom at an aceeleration of 0.45 m/s^2 forward for 1.3s, how fast would she be going after 1.3 seconds if he had started with a velocity of 0.25 m/s forward?

Homework Equations


d = (v1+v2/2)t
a = v2 - v1 /t


The Attempt at a Solution


so we're looking for V right? Which would be v1 & v2.
v2 - v1 = at
= 0.25 x 1.3
= 0.325

but the answer here says 0.84 m/s forward.

What am I doing wrong? Please help, thank you so much.

But what we're looking for is "how fast would she be going after the 1.3 s" isn't that the speed?
It is the velocity after the 1.3 s have elapsed, which is v2 in the equation you used. And v1 is the velocity at the beginning of the 1.3 s -- and they tell you what it is in the problem statement. They also tell you what the values of a and t are.

To summarize:

v2 - v1 = a t, as you said.

You are trying to find v2. You are told what everything else in the equation is.
 

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