Projectile Question Physics 12

In summary, the projectile is launched with a speed of 48 m/s at an angle of 34 degrees BELOW the horizontal. The velocity of the projectile after 2.5 seconds is less then the initial (which is 48 m/s).
  • #1
jonniechung
4
0

Homework Statement



Hi, I am just wondering if someone can check if this is the correct answer for this question. Thanks in advance

1 . A projectile is launched with a speed of 48m/s at an angle of 34 degrees BELOW the horizontal. Calculate the speed an direction of the projectile 2.5 seconds after launch. Ignore friction.


Homework Equations



x/y component . addition of vectors. v=vo+at

The Attempt at a Solution




This is my answer : 40 m/s at 3.3 degress South of East

I find it surprising that the final velocity of the projectile is less then the initial (which is 48m/s).


Here it is:

48 sin 34 = -26.8m/s
48 cos 34 = 39.8

v = vo +at

v = -26.8 + (9.8)(2.5) <--- + acceleration because motion is towards center of Earth

v = -2.3

From here I used addition of vectors in x/y component

x = 39.8
y = -2.2

After 2.5 seconds

Answer: vf = 40 m/s at an angle of 3.3 degrees <---- tan theta


Shouldn't the vf of the projectile (after 2.5 seconds) be greater then the vo? Since it has a + 9.8 m/s ^ 2 .

Thank you
 
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  • #2
v = -26.8 + (9.8)(2.5) <--- + acceleration because motion is towards center of Earth
You need a minus sign on the 9.8. The 26.8 and the 9.8*2.5 are both downward.
For the direction, you'll get an angle below horizontal - no "South of East"
 
  • #3
Delphi51 said:
You need a minus sign on the 9.8. The 26.8 and the 9.8*2.5 are both downward.
For the direction, you'll get an angle below horizontal - no "South of East"

Thank you very much. The correct answer should be 65 m/s , 55 degrees below horizontal ?
 
  • #4
I got 64 m/s and 51 degrees, but I used g = 9.81.
Might be worth checking the angle again - that's quite a difference.
Did you have 49.7 for the vertical velocity?
 
  • #5
Nope, i got 51.4 m/s...

But... it was 52 degrees. I don't know why i put down 55 degrees lol

Thanks
 

1. What is a projectile?

A projectile is any object that is launched or thrown into the air and is subject to the force of gravity. Examples include a baseball, a bullet, or a rocket.

2. What factors affect the trajectory of a projectile?

The trajectory of a projectile is affected by its initial velocity, the angle at which it is launched, and the force of gravity. Air resistance may also play a role, depending on the object's shape and speed.

3. How do you calculate the range of a projectile?

The range of a projectile can be calculated using the formula R = (v2sin2θ)/g, where R is the range, v is the initial velocity, θ is the launch angle, and g is the acceleration due to gravity.

4. Can a projectile reach its initial height?

Yes, a projectile can reach its initial height if it is launched at an angle of 90 degrees. However, in most cases, a projectile will not reach its initial height due to the force of gravity pulling it down.

5. How does air resistance affect a projectile's motion?

Air resistance can affect a projectile's motion by slowing it down and changing its trajectory. This is especially noticeable for objects with a large surface area, such as a feather or a parachute, which experience more air resistance than a smaller and more streamlined object, like a bullet.

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