Projectile Motion - Horizontal Launch

In summary, a stone is thrown horizontally at 5.0 m/s from the top of a cliff 78.4 m high. The stone takes 4 seconds to reach the bottom of the cliff and strikes the ground 20 meters from the base of the cliff. The question also asks for the horizontal and vertical components of the velocity of the stone just before it hits the ground, which can be found using equations involving velocity and acceleration. The concept of component vectors is important in solving this problem.
  • #1
bkoiskewl1
7
0

Homework Statement


A stone is thrown horizontally at 5.0 m/s from the top of a cliff 78.4 m high.
a. How long does it take the stone to reach the bottom of the cliff?
b. How far from the base of the cliff does the stone strike the ground?
c. What are the horizontal and vertical components of the velocity of the stone just before it h its the ground?


Homework Equations



a. yf = yi + vyi t + (1/2)at^2
b. xf = xi + vxi t
c. ?



The Attempt at a Solution


a. 0 = 78.4 + 0 - 4.9t^2
78.4 + 0 - 4.9t^2
-4.9t^2 = -78.4
t= 4 sec...is this correct?

b. xf = 0 + 5m/s(4 sec)
= 20 m..is this correct??

c. I have no idea how to do this please help
 
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  • #2
bkoiskewl1 said:
c. I have no idea how to do this please help

Do you know any equations that involve velocity and acceleration?
 
  • #3
i don't know what the question is asking for
 
  • #4
bkoiskewl1 said:
i don't know what the question is asking for

Can you explain a bit more about exactly what it is you don't get? Is it the meanings of some of the words, or something else?
 
  • #5
heth said:
Can you explain a bit more about exactly what it is you don't get? Is it the meanings of some of the words, or something else?

I guess its the meaning of the words...what kind of answer are they asking for..?
 
  • #6
bkoiskewl1 said:
I guess its the meaning of the words...what kind of answer are they asking for..?

Do you know what a "component" is? Also called a "component vector" sometimes? If not, it's probably an idea to read about them in your textbook, then come back to the question and see if it makes more sense.

(You already used some components in your solutions to the earlier parts of the question, but probably without calling them that yourself! It's well worth the time spent, as you'll be using them all the time later on in your course.)
 
  • #7
Could you tell me what it is...? I don't have my book with me..
 
  • #8
bkoiskewl1 said:
Could you tell me what it is...? I don't have my book with me..

Google is your friend. This is the first hit when you search for "component vector"

http://id.mind.net/~zona/mstm/physics/mechanics/vectors/findingComponents/findingComponents.htm
 
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Related to Projectile Motion - Horizontal Launch

1. What is projectile motion?

Projectile motion is the motion of an object that is launched into the air and then moves along a curved path due to the influence of gravity. It follows a parabolic trajectory, meaning it moves in a curved path that is symmetrical around a central axis.

2. What is a horizontal launch?

A horizontal launch is when an object is launched horizontally, meaning it starts with an initial velocity in the horizontal direction and does not have any initial velocity in the vertical direction. This type of launch is often used in projectile motion experiments to isolate the effects of gravity on the object's motion.

3. What factors affect the range of a horizontal launch?

The range of a horizontal launch is affected by the initial velocity, the launch angle, and the acceleration due to gravity. The higher the initial velocity and the smaller the launch angle, the greater the range will be. The acceleration due to gravity, which is a constant value, also plays a role in determining the range of a horizontal launch.

4. How does air resistance affect horizontal launch?

Air resistance, also known as drag, affects the motion of an object in a horizontal launch by slowing it down. This is because the object experiences a force in the opposite direction of its motion due to the air molecules colliding with it. As a result, the object's range will be shorter and its flight time will be longer compared to a launch in a vacuum where there is no air resistance.

5. Can a horizontal launch ever have the same range as a launch with an angle?

No, a horizontal launch will never have the same range as a launch with an angle. This is because a launch with an angle has both horizontal and vertical components of motion, allowing it to travel a greater distance compared to a horizontal launch which only has a horizontal component of motion. Additionally, the angle at which the object is launched can be adjusted to maximize its range, while a horizontal launch is limited by its initial velocity and the acceleration due to gravity.

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