I need some physics help please, ladies and gentlemen?

Question

1. Before a collision, a 28 kg object is moving at +10 m/s. Find the impulse that acted on the object if, after the collision, it moves at the following speeds.

(a) +8.0 m/s

____N·s

(b) -8.0 m/s

____ N·s

(the answers are not 56 or 504)

2.Small rockets are used to make tiny adjustments in the speed of satellites. One such rocket has a thrust of 35 N. If it is fired to change the velocity of a 71700 kg spacecraft by 64 cm/s, how long should it be fired?

____min

(answer is not 1311)

3.An animal-rescue plane flying due east at 36.0 m/s drops a bale of hay from an altitude of 69.4 m. If the bale of hay weighs 189 N, what is the momentum of the bale the moment before it strikes the ground? Give both magnitude and direction.

____kg·m/s

____° (below the horizontal)

Even if you dont get the answers, some guidance would be greatly appreciated! thank you in advance for any help! :)

Answer 1

1.  Newtons are kilogram meters per second squared, so you're trying to find [kg meters per second] (Newton times second). So...

28 kg object, total velocity change of -2.0 m/s

if you multiply 28 kg times -2.0 m/s you get

   -56 kgm/s   =   -56 Ns

that's your impulse. make sure you have the negative.

For the next part you just make the velocity change -18.0 m/s and do the same procedure.

2.  This is just doing #1 backwards.

First, change velocity to m/s:

64 cm/s  x  1/100 m/cm (conversion factor)  =  0.64 m/s

Now find the total impulse needed:

71700 kg  x  0.64 m/s  =  4589 kgm/s

Now divide total impulse needed by the force that the rocket exerts:

4589 kgm/s divided by 35 N  =  1311 seconds

But don't forget the answer must be in minutes:

1311 s   x   1/60 min/s (conversion factor)  =  22 min (preserve significant figures)

3 is tough. Let's see if I can remember...

I don't have the formulas I'd normally use, so I'll have to do the first part weird.

2.661 s  x   9.8 m/s2   =   26.08  m/s

the  best way to go from here is to use vectors.

using vectors you get:

44.454 m/s  at   35.92 degrees below horizontal.

from there convert velocity into momentum:

189 N   /   9.8 m/s2   =   19.286 kg

44.454 m/s  x  19.286 kg  =  279 kg m/s (remember sig. fig.s)

at 35.9 degrees below horizontal

I'm gonna go get some dinner now.