# Homework Help: Altitude in time

1. Sep 9, 2015

### Manh

1. The problem statement, all variables and given/known data
A spaceship lifts off vertically with constant acceleration and reaches a speed of 340 km/hin 1.1 min .
What is the ship's altitude at t = 66 s ?
Express your answer to two significant digits and include the appropriate units.
2. Relevant equations
xf = xi + v*delta t

3. The attempt at a solution
6233.04 m

2. Sep 9, 2015

Chet

3. Sep 9, 2015

### DaniV

You need to find the acceletion of the spaceship,after this put this data in equzion that describe his state according the time including acceleration parameter,
Can you find this equzion?

4. Sep 9, 2015

### Manh

I convert 340 km/h to 94.44 m/s and 1.1 min to 66 s.
I plug the known data to the equation:
xf = 0 + (94.44)(66)
xf = 6233.04 m

5. Sep 9, 2015

### Staff: Mentor

You plugged in the final velocity, but was it travelling with that velocity the whole time? What was the average velocity, given the acceleration was constant?

Chet

6. Sep 9, 2015

### DaniV

This equation doesn't describe the body in acceleration...

7. Sep 9, 2015

### Manh

a = 94.44/66 = 1.43 m/s^2
xf = xi + vi*t + 1/2at^2
xf = 0 + (94.44)(66) +1/2(1.43)(66)^2
xf = 9347.58 m

8. Sep 9, 2015

### DaniV

Thats right!!!

9. Sep 9, 2015

### Manh

So to express the answer in two sig figs, it should be 9.3 x 10^3 m?

10. Sep 9, 2015

### Manh

I submit the answer but it is still incorrect according to Mastering Physics

11. Sep 9, 2015

### Staff: Mentor

This is incorrect. The initial velocity is zero. Only the 3rd term should be in there. Alternately, the average speed is (94.44)/2 = 47.22 m/sec, so the distance should be half your original answer 6233/2 = 3117 m. Either way, you will get the same answer.

Chet

12. Sep 9, 2015

### Manh

I would check my answer again. Thanks!

13. Sep 9, 2015

### DaniV

The initial velocity is zero due to the fact that it say to us that spaceship accelerate from zero to 340 km/h