Aeroplane Projectile Homework: Determine Velocity

  • Thread starter Ahmad Hossain
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    Projectile
In summary: But for the sign of the vertical velocity, you need to distinguish between motion upward and motion downward. Check that please.Also, your components should have units, for example m/s.And your final answers should be a bit more specific, i.e. a bit more informative. I hope you don't mind giving it a try.In summary, the bird has a horizontal velocity of 11.76 m/s and a vertical velocity of -14 m/s at impact with the windscreen, with the angle of impact being 50 degrees from the horizontal.
  • #1
Ahmad Hossain
29
2

Homework Statement



A windscreen is dirty and a bird dropped something which hits perpendicular your windscreen (Which has an inclination angel 40°). By comparison with the height of your house you know the flight height of the bird quite well. 10 m above your car. Determine the Horizontal flight velocity of the bird? we are ignoring friction... Find out also...Time for falling 15m... Vertical velocity after dropping 15m...Required Horizontal velocity[/B]

Homework Equations

and attempt
Time for free fall after dropping 15m

y= Vot - 0.5 x 9.81 t^2 (g= -9.81m/s2) (y=15m) (Vo= initial velocity is 0)
t= 3s. ( by calculation)

Vertical velocity after dropping 15m...

v= Vo + gt
= 0 + 9.81 m/s^2 X 3s
= 29.43s[/B]

The Attempt at a Solution


but I think my method is wrong.

I can use also by this way,
Horizontal velocity Vx = Vxo
Vertical velocity Vy = Vyo - gt

Basically i am not sure that my method to solve the question is ok [/B]
 
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  • #2
Hello Ahmad, welcome to PF.

This is a nicely different exercise from the usual projectile problems. You really want to sort out things and make a plan how to come to the solution. A drawing would be very helpful.

What do you know ?

From the exercise text:
The dropping is from a height of 10 m. Not 15 m as you seem to think (why?)
The angle of the trajectory at the moment of impact is 50 degrees wrt horizontal ( ##\perp## the 40##^\circ## windscreen ).​

From your textbook or your lecture notes, or from here :
In the horizontal direction there is uniform motion with constant speed( horizontal v0 of the bird ).
In the vertical direction there is uniformly accelerated motion with constant acceleration ##\ \vec g = -9.81\ ## m/s, starting with 0 m/s as you stated.​

Combine all these goodies in a few compact equations. Your start (find t) is the right approach. And you do already have the right expressions (partly in numbers, partly in symbol) for the velocities at impact in your attempt at solution. Those give you an angle and bingo ! Good luck.
 
  • #3
you are right but I need the exact solution.....I draw the trajectory and I understand quite well but don't mind. I need the exact solution of Horizontal and vertical velocity...
I can compare my solution....Thanks a lot
 
  • #4
If I consider 10 m height and I get t = 2.03s and vertical velocity = 19.91 m/s. and Horizontal velocity = 0
 
  • #5
Can't be right. The dropping has to be 'launched' with a nonzero velocity and it has to land at a 50##^\circ## angle, not vertically.
 
  • #6
Can you explain please and write the solution. Yes I get what you mean but I really do not know how to get Horizontal velocity...
 
  • #7
And the 2.038 isn't right either. Can you show how you calculate it ? What equation ? What are the dimensions ?
 
  • #8
X= Vot - 0.5 gt^2
10m = 0 - 0.5 x 9.81 x t^2
t = 1.43 s.

Vertical velocity
V= Vo + at
=0 - 9.81 x 1.43s
= -14m/s

and Horizontal velocity ?​
 
  • #9
ok, t for 10m drop is okay, so is the vertical velocity ... 9.81 has units m/s2 , here as an acceleration.
is the horizontal velocity faster than 14m/s , or slower than 14m/s ? (how does it hit?)
 
  • #10
Ahmad Hossain said:
X= Vot - 0.5 gt^2
10m = 0 - 0.5 x 9.81 x t^2
t = 1.43 s. right. I think previously in post #4 you had t2 here.

Vertical velocity
V= Vo + at
=0 - 9.81 x 1.43s
= -14m/s

and Horizontal velocity ?​
You now have one component of the velocity at impact on the windshield. The angle at landing is prescribed and that determines the other component !
 
  • #11
I get Vy= 14 m/s and Vx = 11.76 for example, tan 40° = Vy/Vx Vx= 11.76 is it right? last but not least, I am really thankful who help me to solve it out
 
  • #12
Ahmad Hossain said:
I get Vy= 14 m/s and Vx = 11.76 for example, tan 40° = Vy/Vx Vx= 11.76 is it right? last but not least, I am really thankful who help me to solve it out
The magnitudes look good.
 

FAQ: Aeroplane Projectile Homework: Determine Velocity

1. What is an aeroplane projectile?

An aeroplane projectile is an object that is launched or dropped from an aircraft and is subject to the forces of gravity and air resistance.

2. Why is it important to determine the velocity of an aeroplane projectile?

Determining the velocity of an aeroplane projectile is important for a variety of reasons, including understanding its trajectory, predicting its impact point, and assessing its potential danger. It can also help in designing and testing aircraft and other projectiles.

3. What factors affect the velocity of an aeroplane projectile?

The velocity of an aeroplane projectile can be affected by several factors, including the initial launch speed, the angle of launch, air resistance, and the weight and shape of the projectile.

4. How is the velocity of an aeroplane projectile calculated?

The velocity of an aeroplane projectile can be calculated using the equation v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration due to gravity, and t is the time the projectile has been in motion.

5. What are some real-world applications of determining the velocity of an aeroplane projectile?

Determining the velocity of an aeroplane projectile has many practical applications, including in military operations, space exploration, and sports such as baseball and golf. It is also useful in understanding the potential impact of natural disasters, such as volcanic eruptions or asteroid impacts.

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