Please help me with these 2 momentum questions. I really really need it. ?

Question

1. A bicycle has a mass of 180 kg. If it has a velocity of 8 m/s northward,

a.) what is its momentuM?

b.) How long must a force of 100 N act on the bicycle to give it this momentum?

2. A car has a mass of 1800 kg. It is traveling at a velocity of 17 m/s northward. A gravel-and-sand delivery truck with a mass of 3000 kg moving at 20 m/s southward collided head-on with the car. They stick together upon colliding with each other. Find their common velocity after the collision.

Please explain how you get the answer to me. We have a quiz tomorrow, you see, and more than I need the answer, I need to learn. I just can't understand my teacher. = ( Please help me.

Thank you so much!

Answer 1

1.a)momentum= mass x velocity = 180x8= 1440 kg m/s. (b) impulse =change in momentum ; 100xt =1440 ;t=14.4sec.

2)applying conservation of linear momentum 1800x7 --3000x20 =4800v; v=9.875m/s. In the  problem the negative sign due to the fact that the momentum of vehicles is in the opposite direction.

Answer 2

1a) Momentum is a mass in motion.  So, it is the mass times velocity.  Momentum is a vector quantity.  That means direction is a part of momentum.  

p = mv

p = 180kg * 8 m/s

p = 960 kg * m/s

1b)  F = m * a  (f = force, m = mass, a = acceleration)

a = v/t ( v= velocity, t = time)

F = m * v/t

100N = (m*v)/t

100 = p/t

100 = 960/t

t = 9.60 seconds

2)  Let's use the equation:

M1V1 + M2V2 = (M1 + M2)Vf

(this equation is there because the first, the masses and the velocities are different.  After the equal sign, the masses are stuck together at some common velocity)

M1 = 1800kg

V1 = 17m/s

M2 = 3000kg

V2 = 20m/s

Vf = velocity after collision.

You can solve it, I'm sure.

Answer 3

momentum is mass*velocity so the bikes momentum is simply

momentum=m*v

momentum= (18 kg)(8 m/s)

momentum= 144 kg*m/s

Force=(Δmomentum/Δt)

momentum=P

Force=(Pf-P0)/(tf-t0)

100N= (144 kg*m/s)/(Δt)

(100 N)Δt=144 kg*m/s

Δt=(144 kg*m/s)/(100 N)

Δt=1.44 s

Note that since the velocity of the car is going north it is + because the velocity of the truck is going south it i -.   Also note that since the car and truck stick together after the collision their masses will be added together so the equation used will be

(mc)(vc0)+(mt)(mt0)=(mc+mt)(vf)

2) Given for the Car: Mass= 1800 kg, v0= 17 m/s

Given for the Truck: Mass= 3000 kg, v0= -20 m/s

(mc)(vc0)+(mt)(mt0)=(mc+mt)(vf)

(1800 kg)(17 m/s)+(3000 kg)(-20 m/s)=(1800 kg+3000 kg)(vf

30600 kg*m/s -6000 kg*m/s =(4800 kg)vf

-29400 kg*m/s=(4800 kg)vf

(-29400 kg*m/s)/(4800 kg)=vf

-6.1 m/s=vf

because the velocity is negative the cars momentum is going southward

so the answer is 6.1 m/s southward