I don't understand how to solve for this problem:
A bicyclist accelerates at 0.89 m/s^2 during a 5.0 s interval. What is the change in the speed of the bicyclist and the bicycle?
Am I supposed to figure out the final or initial velocity? I am really confused. Here's another example:
A train traveling with a speed of 18.0 m/s begins braking as it approaches a train yard. The train's acceleration while braking is -0.33 m/s^2. What is the train's speed after 23 s?
Again, I'm not sure which variable to solve for. Please help!
A bicyclist accelerates at 0.89 m/s^2 during a 5.0 s interval. What is the change in the speed of the bicyclist and the bicycle?
Am I supposed to figure out the final or initial velocity? I am really confused. Here's another example:
A train traveling with a speed of 18.0 m/s begins braking as it approaches a train yard. The train's acceleration while braking is -0.33 m/s^2. What is the train's speed after 23 s?
Again, I'm not sure which variable to solve for. Please help!
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Suppose he starts at zero.
vi = 0
vf = ???
t = 5.0 second
a = 0.89 m/s^2
formula
a = (vf - vi) / t
0.89 = vf / 5
vf = 4.45 m/s
The change is also 4.45.
Well, you could argue, that works if you make vi = 0. What happens if it's not? Suppose you start it out at "a" meters per second.
vi = a
vf = ???
a = 0.89 m/s^2
t = 5 seconds
a = (vf - vi)/t
0.89 * 5 = vf - a
4.45 + a = vf. But what is the change? Change = vf - vi = 4.45 + a - a = 4.45. Same as before.
Problem 2
========
vi = 18 m/s
vf = ??
a = - 0.33 m/s^2
t = 23 sec
a = (vf - vi)/t
-0.33 m/s^2 = (vf - 18) / 23
- 7.59 = vf - 18
- 7.59 + 18 = vf
10.41 = vf
vi = 0
vf = ???
t = 5.0 second
a = 0.89 m/s^2
formula
a = (vf - vi) / t
0.89 = vf / 5
vf = 4.45 m/s
The change is also 4.45.
Well, you could argue, that works if you make vi = 0. What happens if it's not? Suppose you start it out at "a" meters per second.
vi = a
vf = ???
a = 0.89 m/s^2
t = 5 seconds
a = (vf - vi)/t
0.89 * 5 = vf - a
4.45 + a = vf. But what is the change? Change = vf - vi = 4.45 + a - a = 4.45. Same as before.
Problem 2
========
vi = 18 m/s
vf = ??
a = - 0.33 m/s^2
t = 23 sec
a = (vf - vi)/t
-0.33 m/s^2 = (vf - 18) / 23
- 7.59 = vf - 18
- 7.59 + 18 = vf
10.41 = vf
-
you're not looking for the initial or final velocity. you're looking for the change in velocity (commonly displayed as the greek letter delta (Δ), so it would be Δv). the change in velocity is equal to final velocity minus initial velocity. However, it really doesn't matter what speed the bicyclist started at, you'd end up with the same answer. That's why they don't give initial velocity in the problem.
Δv=at
this equation ^ can actually be found by this equation: v₂=at+v₁. subtraction v₁ will allow you to substitute Δv in for v₂-v₁
you are given acceleration (a) and you are given time (t). you just solve.
for the second one just use v₂=at+v₁. In this one you are solving for the final velocity (or v₂).
It's just equations. they aren't hard. it's just plugging in numbers. What your priority should be though, is to understand the concept of acceleration. It should help you out in the future.
Δv=at
this equation ^ can actually be found by this equation: v₂=at+v₁. subtraction v₁ will allow you to substitute Δv in for v₂-v₁
you are given acceleration (a) and you are given time (t). you just solve.
for the second one just use v₂=at+v₁. In this one you are solving for the final velocity (or v₂).
It's just equations. they aren't hard. it's just plugging in numbers. What your priority should be though, is to understand the concept of acceleration. It should help you out in the future.