What is the equation for displacement of a jet?

Physics Questions? Ask them here!
Post Reply
RusselMank
Posts: 2
Joined: Mon Oct 01, 2018 12:54 pm

What is the equation for displacement of a jet?

Post by RusselMank » Mon Oct 01, 2018 1:45 pm

The statement of the problem is below. The first thing is they give us the initial velocity at the start time, and it is assumed that it accelerates at a constant rate. There is no air resistance,and the jet ends up going at 435m/s, which actually is the fnal velocity of the jet.

The initial velocity of a military jet is 235 m/s eastward. Thepilot ignites the afterburners, and the jet accelerates eastward at a constat rate for 1.70 s. The final velocity of the jet is 435 m/s eastward. What was the jet's displacement during the time it was accelerating?

However, I don't know what kind of equation to use for displacement.

jeff
Site Admin
Posts: 38
Joined: Mon Mar 05, 2018 11:54 pm

Re: What is the equation for displacement of a jet?

Post by jeff » Mon Oct 01, 2018 1:53 pm

Hi RusselMank,
RusselMank wrote:
Mon Oct 01, 2018 1:45 pm
The statement of the problem is below. The first thing is they give us the initial velocity at the start time, and it is assumed that it accelerates at a constant rate. There is no air resistance,and the jet ends up going at 435m/s, which actually is the fnal velocity of the jet.

The initial velocity of a military jet is 235 m/s eastward. Thepilot ignites the afterburners, and the jet accelerates eastward at a constat rate for 1.70 s. The final velocity of the jet is 435 m/s eastward. What was the jet's displacement during the time it was accelerating?

However, I don't know what kind of equation to use for displacement.
For this problem, there is only one motion that we have to deal with so one way to approach it is by carefully listing the values and variables they give and the quantity they are asking for. For example, for this problem we might write

t = 1.7 s
v_i = 235 m/s
v_f = 435
x = ?

Notice that we are not given acceleration, and that is not what we are trying to find. Do you see a kinematic equation that only has the four variables above (and does not have acceleration)?

RusselMank
Posts: 2
Joined: Mon Oct 01, 2018 12:54 pm

Re: What is the equation for displacement of a jet?

Post by RusselMank » Mon Oct 01, 2018 2:16 pm

It's hard to guess, but I saw this one

d = 1/2*(vo+vf)*t

Is that right?

jeff
Site Admin
Posts: 38
Joined: Mon Mar 05, 2018 11:54 pm

Re: What is the equation for displacement of a jet?

Post by jeff » Mon Oct 01, 2018 2:19 pm

RusselMank wrote:
Mon Oct 01, 2018 2:16 pm
It's hard to guess, but I saw this one

d = 1/2*(vo+vf)*t

Is that right?
Yes, that will work! If you plug in your values, that should give you the final answer. What do you get for that?

Post Reply