Finding time when you have initial velocity and position

In summary: You also have gravity acting on the rocket. You can use the equations you know for projectile motion to determine the time it takes for the rocket to reach its maximum height and the horizontal range it covers.
  • #1
oliampian
6
0
***Sorry I meant to say finding time when you have initial velocity and position***
1. Homework Statement

A test rocket is launched by accelerating it along a 200.0-m incline at 1.36 m/s2 starting from rest at point A (the figure (Figure 1) .) The incline rises at 35.0 ∘ above the horizontal, and at the instant the rocket leaves it, its engines turn off and it is subject only to gravity (air resistance can be ignored).

Find the maximum height above the ground that the rocket reaches.
Find the greatest horizontal range of the rocket beyond point A.

Known:
Vo = 0 (because starting from rest)
aon incline = 1.36 m/s2
aoff incline = -9.8 m/s2
ramp distance = 200m
θ = 35°

Homework Equations


x = xo + Vot + (0.5)at2
V = Vo + at
V2 = Vo2 + 2aΔx

The Attempt at a Solution


I already found the first part, which turned out to be 124m when rounded to three sig figs.
I found through calculations that Vat end of incline = 23.323m/s:
using the V2 = Vo2 + 2aΔx
Vat end of incline = √(2(1.36m/s2)(200m))
Vat end of incline(x-component) = 23.323m/s(sin(35)) = 19.1050m/s
Distance in x-component = Dx = 200m(cos35) = 163.8304

So to find the total horizontal distance so far I have the equation:
x = 163.8304 + 19.105t - 0.5(9.8)t2

What I'm stuck on is trying to find the total time so I can plug that into the equation.
 
Last edited:
Physics news on Phys.org
  • #2
oliampian said:
***Sorry I meant to say finding time when you have initial velocity and position***
1. Homework Statement

A test rocket is launched by accelerating it along a 200.0-m incline at 1.36 m/s2 starting from rest at point A (the figure (Figure 1) .) The incline rises at 35.0 ∘ above the horizontal, and at the instant the rocket leaves it, its engines turn off and it is subject only to gravity (air resistance can be ignored).

Find the maximum height above the ground that the rocket reaches.
Find the greatest horizontal range of the rocket beyond point A.

Known:
Vo = 0 (because starting from rest)
aon incline = 1.36 m/s2
aoff incline = -9.8 m/s2
ramp distance = 200m
θ = 35°

Homework Equations


x = xo + Vot + (0.5)at2
V = Vo + at
V2 = Vo2 + 2aΔx

The Attempt at a Solution


I already found the first part, which turned out to be 124m when rounded to three sig figs.
I found through calculations that Vat end of incline = 23.323m/s:
using the V2 = Vo2 + 2aΔx
Vat end of incline = √(2(1.36m/s2)(200m))
Vat end of incline(x-component) = 23.323m/s(sin(35)) = 19.1050m/s
Distance in x-component = Dx = 200m(cos35) = 163.8304

So to find the total horizontal distance so far I have the equation:
x = 163.8304 + 19.105t - 0.5(9.8)t2

Where does this equation come from? And when did gravity start acting sideways?

When the rocket leaves the ramp, the engines turn off, so the rocket just coasts until it lands.

What I'm stuck on is trying to find the total time so I can plug that into the equation.

When the rocket leaves the ramp, it acts like any other projectile. You have an initial velocity and an angle at which the rocket is traveling relative to the horizon.
 

1. What is the equation for finding time with initial velocity and position?

The equation for finding time when you have initial velocity and position is t = (x-x0) / v0, where t is time, x is final position, x0 is initial position, and v0 is initial velocity.

2. Can this equation be used for any type of motion?

No, this equation can only be used for motion with constant velocity. If the velocity changes, a different equation must be used.

3. How do I know if I need to use this equation?

If you have an object that starts at a specific position and moves at a constant velocity, then you can use this equation to find the time it takes to reach a certain position.

4. What units should be used for the variables in this equation?

The units for time (t) should be in seconds (s), position (x and x0) should be in meters (m), and velocity (v0) should be in meters per second (m/s).

5. Is there any other information needed to use this equation?

Yes, in addition to the initial velocity and position, you also need the final position (x) to solve for time. Without this information, the equation cannot be used.

Similar threads

  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
18
Views
2K
  • Introductory Physics Homework Help
Replies
10
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
4K
  • Introductory Physics Homework Help
Replies
1
Views
4K
  • Introductory Physics Homework Help
Replies
1
Views
2K
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
21
Views
2K
  • Introductory Physics Homework Help
Replies
5
Views
6K
  • Introductory Physics Homework Help
Replies
2
Views
1K
Back
Top