View Poll Results: if two different masses have equal kinetic energy, they must not have equal momentum.
True 4 80.00%
False 1 20.00%
Voters: 5. You may not vote on this poll

Projectile Motion's relationship with Kinetic Energy and Potential Energy

by Whakataku
Tags: kinetic energy, potential energy, projectile motion, range
Whakataku is offline
Oct7-11, 01:01 AM
P: 12
Imagine a ramp setup on top of a tall table. The height Δy is measured. To find the initial velocity at the instant the ball leaves the ramp, I set up the kinetic energy and potential energy equal to each other to find the initial velocity of the x component.

m*g*(hr) = 0.5*m*v^2

where hr is the height of the ramp and v is initial velocity (x-component)

solving for vx (x-component velocity), I got:
vx = √(2*g*hr)

To get the time for the object's time in flight:
y'-y= vy + 0.5gt^2
Δy= vy + 0.5gt^2, where Δy is the height from the ground to the ramp.
since θ= 0 I found t to be:
t = √{ (2*∆y)/g }

Now my question is how do I find the range of this object?
I started out with Δx = vx*t ; where vx is the initial x-component velocity.... is that even right?
I'm hesitant to use it because written as Δx/t, it looks like an average velocity equation.
Furthermore, in Wikipedia I saw the equation

d= {v*cos([itex]\Theta[/itex])}/g * [v*sin([itex]\Theta[/itex]) + sqrt(v*sin([itex]\Theta[/itex])^2+2g*y)]
under uneven ground

but the problem is I don't have final velocity................ or can I calculate the final velocity with the givens........ if so how??

Could anyone please nudge me in the right direction to find Δx?

Phys.Org News Partner Physics news on
Physicists consider implications of recent revelations about the universe's first light
Vacuum ultraviolet lamp of the future created in Japan
Grasp of SQUIDs dynamics facilitates eavesdropping
Whakataku is offline
Oct7-11, 01:19 PM
P: 12
I think I solved it........... duh.

in the distance formula
d = v(initial)*t + 1/2*a*t^2.

v(initial) and time is already attained and the the a acceleration is -9.81m/s^2

Correct me if I'm wrong.

Register to reply

Related Discussions
The relationship between potential energy and kinetic energy General Physics 7
Relationship between Kinetic Energy and Gravitational Potential Energy. Introductory Physics Homework 1
Kinetic energy / projectile motion question Introductory Physics Homework 15
Projectile motion and kinetic energy Introductory Physics Homework 6
Kinetic Energy, Momentum, Projectile Motion ( A real stumper ) Introductory Physics Homework 47