• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

A little physics Help

F

Finns14

Golden Member
Ok here is the problem and answer

A 0.970-kg ball is dropped from rest at a point 4.60 m above the floor. The ball rebounds straight upward to a height of 2.60 m. Taking the negative direction to be downward, what is the impulse of the net force applied to the ball during the collision with the floor?

Number
16.134872616543 Units kg·m/s

Ok I think that I have to find the velocities but I can figure out how to do that. The bounce is confusing me quite a bit.

http://edugen.wiley.com/edugen/courses/crs1000/art/math/c07/math010.gif

Thats the equation I need but I dunno how to get there. Thanks
 
velocity down can be found using mgh1= 1/2mv1^2

velocity bakc up can be f ound using mgh2=1/2mv2^2
 
yeah I know how to calcualte impules once I get the velocities but that is where I was having a problem
 
Originally posted by: Finns14
why are masses on both sides of the equations wouldn't they cancel?
Click to expand...

yeah, im just using hte most basic energy equation to make it clear that potential energy = kinetic energy when the ball goes from top to bottom and vice versa
 
Originally posted by: Finns14
why are masses on both sides of the equations wouldn't they cancel?
Click to expand...

Yes, the masses cancel....what does this tell you? that the acceleration due to gravity and the velocity of the object is NOT affected by it's mass, only forces are affected by mass.


EDIT: case in point, the experiment where a feather and a rock are put in a tube with all the air sucked out. They both drop at the same rate and hit the bottom of the tube at the same time, going the same velocity. Mass doesn't matter when it comes to velocity/acceleration, only when it comes to force.
 
Originally posted by: Finns14
Yeah I was just confused as to why this equation was being used
Click to expand...

You also could have used the kinematic equations but they're basically just energy equations rewritten
 
I also need the delta T which they don't give me


Edit do I need to use one of the basic equation once I calculate the v's?
 
Originally posted by: Finns14
Originally posted by: Mo0o
vf^2 = vi^2 + 2*a*d
Click to expand...

that equations doesn't give me force though
Click to expand...

Do you need the force? If you can find v down and v up, you can find the impulse and that's all it asks for. Since you dont know deltaT(which is really really small) you can't really find the force either
 
I am sorry my professor is pretty bad this is the first class he ever taught. What is the equation to calculate impulse?
 
Originally posted by: Finns14
I am sorry my professor is pretty bad this is the first class he ever taught. What is the equation to calculate impulse?
Click to expand...

Ok the impulse it's asking for is the force*time applied to the ball as it touches teh groundand bounces back up. Impulse=F*t=delta(Mv). So it's either the amount of force applied for a period of time or the amount of momentum that changes during that time. So to find the amount of impulse applied to the ball, you find the velocity of the ball as it falls and the velocity of the ball as it goes up. You find the change in momentum (make sure to take into account the change in velocity) to find the impulse. You can't use the F*T equation because it doesn't tell you how long teh ball touches the ground nor the force the ball experiences as it touches the ground and what not.
 
OOOOOO ok thank you the impulse is either one half the equation or the other. Since I don't have F and t I can use mass and delta v

Is that right
 
Originally posted by: Finns14
OOOOOO ok thank you the impulse is either one half the equation or the other. Since I don't have F and t I can use mass and delta v

Is that right
Click to expand...

yessir
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top