Question

Suppose a rocket ship accelerates upwards with acceleration equal in magnitude to twice the magnitude of g (we say that the rocket ship accelerations upwards at 2g), but runs out of fuel after 100 seconds, after which point it stops accelerating upward. At this point, the rocket begins accelerating downwards with a magnitude of g. Assume that the gravitational pull of the Earth on the rocket doesn't change with altitude.

a)How high above the surface of the Earth does the rocket travel before it stops accelerating?

b) How fast is the rocket going when it stops accelerating?

c) How high does the rocket get before it begins to fall back to Earth?

d) How long after launch does the rocket strike the Earth again?

e) What is the average velocity of the rocket between when it leaves the Earth and when it strikes the Earth again?

Answer 1

I think so that you have many doubts regarding this large solution so here I am explaining again the solution

In first case we have to find the distance up to the rocket gone for hundred seconds yeh simple formula used second motion equation and we know that initial velocity is zero please refer my solution

in second case we have to find the velocity at that point when the rocket starts the daccelerating .

Now for this we have to find the distance upto which rocket gone which is done in a part now using motion 1st equation we know final velocity which is the velocity of the topmost point of the rocket that will be zero.

And we have given acceleration 2G and time given 100 sec. use this formula to get the answer of the b part.

In C path asking that how much distance rocket will cover when to start the deacclerating .

Use motion third equation we will get the answer c part.

Now depart asking the total time of the journey we have noticed that at time of the ascent and time of the descent will be the same and you will know these terms I think so if you don't know these terms then please come and I will reach explain you again by commenting.

In e part

question asking about the average velocity we know the formula that is total distance divided by total time