What is the speed of the stone just before it hits the ocean?

In summary, a student is seeking help with a webassign question in a physics with calculus (Mechanics) subforum. The question involves a boy throwing a stone horizontally from a cliff and finding expressions for the time, initial speed, speed at impact, and direction of velocity before impact. The student has correctly solved the first two parts, but is having trouble with the third part. They have attempted to use the equations vf=vi+gt and xf=xi+vi(t)+(g/2)(t^2) but are getting an incorrect answer. They believe the correct answer should be vf=g(√(h/(g/2))), but are unsure why webassign is marking it as wrong. The mistake may be related
  • #1
DocDot
1
0
Im sorry I just realized this is in the wrong subforum...

Homework Statement



Hello Everyone! I am new here and am having trouble with this webassign question. I was able to work out the answer to the first two but the last two are giving me trouble. I am not sure if this is right subforum to put this in, but I am in physics with calculus (Mechanics).

A boy throws a stone horizontally from the top of a cliff of height h toward the ocean below. The stone strikes the ocean at distance d from the base of the cliff. In terms of h, d, and g, find expressions for the following.

the time t at which the stone lands in the ocean

the initial speed of the stone

the speed of the stone immediately before it reaches the ocean

the direction of the stone's velocity immediately before it reaches the ocean

Homework Equations



vf=vi+gt
xf=xi+vi(t)+(g/2)(t^2)

The Attempt at a Solution



The answer I got for the first one was √(h/(g/2)) which was right

The second one I got was √((d^2)/(h/(g/2))) which was also right

For the third one I got vf=g(√(h/(g/2))) which I thought was right because vf for the x componet is 0 and the velocity is maximum at tf, however webassign is telling me I am wrong.

Thank you all for the help in advance!
 
Last edited:
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  • #2
If you show your steps leading to your result, the mistake can be better identified.
 
  • #3
DocDot said:
...vf for the x component is 0 ...
Think about this a bit more...what is vf_x just before it hits the ocean?
 

FAQ: What is the speed of the stone just before it hits the ocean?

What is 2D Kinematics?

2D Kinematics is a branch of physics that deals with the motion of objects in two-dimensional space. It involves analyzing the position, velocity, and acceleration of objects in both the x and y directions.

How is 2D Kinematics different from 1D Kinematics?

2D Kinematics deals with motion in two dimensions, whereas 1D Kinematics only deals with motion in one dimension. This means that 2D Kinematics takes into account both horizontal and vertical motion, while 1D Kinematics only considers motion along a single axis.

What are the equations used in 2D Kinematics?

The equations used in 2D Kinematics are the same as those used in 1D Kinematics, such as the equations for position, velocity, and acceleration. However, they are applied separately to the x and y directions and must consider both components of motion.

How is 2D Kinematics used in real life?

2D Kinematics is used in various fields such as engineering, sports, and video game design. For example, engineers use 2D Kinematics to design structures that can withstand forces from multiple directions, while video game designers use it to create realistic movements for characters.

What are some common misconceptions about 2D Kinematics?

One common misconception about 2D Kinematics is that it only applies to objects moving in a perfect horizontal or vertical direction. In reality, 2D Kinematics can be applied to any type of motion in two dimensions, including curved or angled paths. Another misconception is that acceleration is always constant in 2D Kinematics, when in fact it can also vary depending on the direction of motion.

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