Checking My Work: Did I Answer Part e) Correctly?

[Bolter]

Homework Statement

Working out initial speed and inclination of projectile

Relevant Equations

SUVAT equations

Have had a try at answering this question, and want to particularly know if I had done part e) correctly

Here is my workings from the previous parts as I need to use some prior values that I have obtained before to do part e)

For the last part, there were 2 ways that I went about it. First one was using conservation of energy and the second was to use Newtons 2nd law and SUVAT. Both methods gave the same result so I guess that is alright.

Thanks!

 

[BvU]

Hi,

Under c) did you notice it is twice the answer for b) ?
I miss f)
The last part went fine too.

Your work is very neat and impeccable !
(but my index finger hurts from scrolling up and down )

 

[Bolter]

Hi,

Under c) did you notice it is twice the answer for b) ?
I miss f)
The last part went fine too.

Your work is very neat and impeccable !
(but my index finger hurts from scrolling up and down )

Yes I did know that the value of c) is double of b).
Since the trajectory of the projectile is symmetrical about the halfway point (maximum height) on either side.

So time taken to reach from ground to max height is the same as time taken to reach max height to ground. In fact it's just a simple model of a quadratic curve. I just wanted to clarify myself by using SUVAT here

Whoops I did miss part f) That must be a parabola, right?

Haha sorry about the long scrolling. My apologies!

 

[neilparker62]

A couple of useful formula for this type of problem where horizontal range (R) and maximum height (H) of a projectile are given:
$$tanθ=\frac{4H}{R}$$
$$R=\frac{V^2sin(2θ)}{g}\text{ or }V=\sqrt{\frac{Rg}{sin(2θ)}}$$

 

[berkeman]

Haha sorry about the long scrolling. My apologies!

Your work is indeed neat and easier to read than other students who try to post pictures of their work, thanks.

But it still would be good for you to learn to use LaTeX to write your math equations here. And you can print out those equations to turn in as your homework in many circumstances. Here is a nice tutorial for how top use LaTeX:

https://www.physicsforums.com/help/latexhelp/

:-)

 

[gneill]

...and don't forget the LaTeX Guide, a link for which appears just below the bottom left corner of the edit window.