Calculate Change in Momentum of 4.8 kg Mass Launched at 55°

[omc1]

Homework Statement

An object of mass 4.8 kg is projected into the air at a 55° angle. It hits the ground 3.6 s later. What is the magnitude of its change in momentum while it is in the air? Ignore air resistance

Homework Equations

J=p =sumF Δt=mΔv

The Attempt at a Solution

mvsine(theta) = mgt v=43.07 m/s p=mv = 206.74 kg m/s but its says that's wrong i tried it a dif way but got the same answer please help...

 

[kushan]

hello omc1 ,
If you notice momentum will remain conserved along horizontal axis . ie component of velocity along horizontal axis will remain same throughout .
So it will not cause any change in momentum .
Then what will cause a change in momentum ?
When you project the mass upward , the vertical component of mass will vary , and you might also know it will come back with the same speed with which it was thrown .
Try to find out this change

 

[omc1]

so msin(theta)gt=p ??

 

[kushan]

twice of that

 

[omc1]

when i did that it is still giving me a wrong answer ...277.44

 

[HallsofIvy]

With no air resistance, horizontal speed doesn't change and and vertical speed, once the object has hit the ground, will have the same magnitude but opposite sign.

 

[omc1]

the neg of that answer doesn't work either...