Physics 20-1 Final Review: Projectiles

In summary, to calculate how far an object thrown at 16 m/s at an angle of 25 degrees above the horizontal will travel from the base of a 75 m tall building, you must first calculate the time to reach maximum height, which is 16*sin25/g. Then, using the equation y=1/2gt^2, determine the height at maximum height. From there, it is a simple free fall problem to determine the time it takes for the object to hit the ground, which is the total time of the throw. Finally, using the horizontal component of velocity (16*cos25) and the total time, you can calculate the distance the object will travel along the ground.
  • #1
physicznoob
15
0

Homework Statement



A student is standing on the top of a building and he throws an object into the air with a speed of 16 m/s at an angle of 25 degrees above the horizontal. If the building is 75 m tall, how far from the base of the building will the object hit the ground?

Homework Equations



v = d/t
d = vit + 1/2at2

The Attempt at a Solution



i tried to break it up into horizontal and vertical components and break it down into speed, then distance, then time. but nothing i do seems to work.
 
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  • #2
What do you get for the time to max height?
 
  • #3
a = v2 - v1 / t
t = v2 - v1/ a
t = 0 - 16 / -9.81
t = 1.63 s.
 
  • #4
There's your problem right there.

The vertical component of velocity is what must be taken to determine time to max height.

That is 16*sin25.

The horizontal component is 16*cos25.
 
  • #5
i still get the wrong answer...
 
  • #6
where are u setting your zero? the top of the building or the bottom?
 
  • #7
huh? if you mean velocity wise, at the top for vertical motion.
 
  • #8
physicznoob said:
i still get the wrong answer...

So what is your time to max height?

You know that must be 16*Sin25/g = t

And how high is that from launch? y = 1/2 g*t2

Now it is a simple free fall problem to determine the time to hit the ground isn't it?

With the total time ... and the horizontal component of velocity ... viola your distance along the ground.
 

Related to Physics 20-1 Final Review: Projectiles

1. What is a projectile?

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

2. What factors affect the trajectory of a projectile?

The factors that affect the trajectory of a projectile are its initial velocity, angle of launch, and the force of gravity. Other factors such as air resistance and wind can also have an impact.

3. How can you calculate the maximum height and range of a projectile?

The maximum height and range of a projectile can be calculated using the equations:
Maximum Height (h) = (v2sin2θ) / 2g
Range (R) = (v2sin2θ) / g
Where v is the initial velocity, θ is the angle of launch, and g is the acceleration due to gravity.

4. What is the difference between horizontal and vertical motion in projectile motion?

Horizontal motion refers to the motion of a projectile in the x-axis, while vertical motion refers to its motion in the y-axis. In projectile motion, the horizontal velocity remains constant, while the vertical velocity changes due to the force of gravity.

5. What is the importance of understanding projectile motion in real life?

Understanding projectile motion is important in many real-life situations, such as sports, military operations, and space travel. It can also help in predicting the trajectory of objects and making accurate calculations for activities such as shooting or launching rockets.

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