Question

please help, i understand it, but i got confused on the part where it says that they move as one mass or get stuck together

Answer 1

other helper already explains but here are two examples:

2. let N be +ve n S be -ve

N-going Zak momentum=mass*velocity=50*4=200

S-going Zak momentum=40*(-5)=-200

after collision, they get stuck together so their masses=50+40=90

by conservation of momentum:

200+(-200)=90*final vel

0=90*final vel

final vel=0m/s

3. cars have rear end collision so they were traveling in same direction be4

total momentum be4 collision=1200*20+1000*15=39000

cars continue 2 move as 1 mass after collision so final mass=1200+1000=2200

by conservation of momentum, final momentum=2200*final vel=39000

final vel=39000/2200=17.73m/s

plz post in comment if u need 4 n 5

Answer 2

4. Before the dog jumps out, initial momentum=0

After the dog jumps out, final momentum=initial momentum=0

So dog's momentum+canoe's momentum=0

Dog's momentum=mass*velocity

=15*1.2

=18

Canoe's momentum= -(dog's momentum)= -18

Canoe's velocity=-18/40=-0.45m/s

The - sign means the direction is opposity to the dog's jump.

5. Assume the Pennridge player's direction is +ve

Initial momentum before collision=Pennridge player's momentum + Souderton player's momentum

=80*3+70*(-2.5)

=240-175

=65

As they are stuck together after collision, the final mass=80+70=150

Final momentum=Initial momentum=65

Final velocity=Final momentum/Final Mass

=65/150

=0.4333m/s in Pennridge direction