Morning Candice — let's get this done.
Here are the solutions for the collision problem:
3.1:
Step 1: Define a positive direction and list the given values.
Let "towards the right" be the positive direction.
Mass of delivery van (mv) = 5000 kg
Initial velocity of delivery van (vvi) = +10 m/s
Mass of car (mc) = 2000 kg
Initial velocity of car (vci) = −15 m/s (moving left)
Final velocity of car (vcf) = +5 m/s (moving right)
Step 2: Apply the law of conservation of linear momentum.
The total momentum before the collision equals the total momentum after the collision:
mvvvi+mcvci=mvvvf+mcvcf
Step 3: Substitute the values into the equation and solve for vvf.
(5000kg)(+10m/s)+(2000kg)(−15m/s)=(5000kg)vvf+(2000kg)(+5m/s)
50000kg⋅m/s−30000kg⋅m/s=(5000kg)vvf+10000kg⋅m/s
20000kg⋅m/s=(5000kg)vvf+10000kg⋅m/s
20000kg⋅m/s−10000kg⋅m/s=(5000kg)vvf
10000kg⋅m/s=(5000kg)vvf
vvf=5000kg10000kg⋅m/s
vvf=+2 m/s
The magnitude of the velocity of the delivery van immediately after the collision is 2m/s.
3.2:
Step 1: Calculate the total initial kinetic energy of the system.
KEinitial=21mvvvi2+21mcvci2
KEinitial=21(5000kg)(10m/s)2+21(2000kg)(−15m/s)2
KEinitial=21(5000)(100)+21(2000)(225)
KEinitial=250000J+225000 J
KEinitial=475000 J
Step 2: Calculate the total final kinetic energy of the system.
Using vvf=+2 m/s from 3.1 and vcf=+5 m/s.
KEfinal=21mvvvf2+21mcvcf2
KEfinal=21(5000kg)(2m/s)2+21(2000kg)(5m/s)2
KEfinal=21(5000)(4)+21(2000)(25)
KEfinal=10000J+25000 J
KEfinal=35000 J
Step 3: Calculate the change in kinetic energy.
ΔKE=KEfinal−KEinitial
ΔKE=35000J−475000 J
ΔKE=−440000 J
The change in the kinetic energy of the system is −440000J.
3.3:
Since the kinetic energy of the system is not conserved (it changed by −440000 J), the collision is INELASTIC.
3.4:
Step 1: Identify the given values and the impulse-momentum theorem for the car.
Mass of car (mc) = 2000 kg
Initial velocity of car (vci) = −15 m/s
Final velocity of car (vcf) = +5 m/s
Collision duration (Δt) = 0.4 s
The impulse-momentum theorem states that FavgΔt=Δpc=mcvcf−mcvci.
Step 2: Substitute the values into the formula and solve for the average force (Favg).
Favg(0.4s)=(2000kg)(+5m/s)−(2000kg)(−15m/s)
Favg(0.4s)=10000kg⋅m/s−(−30000kg⋅m/s)
Favg(0.4s)=10000kg⋅m/s+30000kg⋅m/s
Favg(0.4s)=40000kg⋅m/s
Favg=0.4s40000kg⋅m/s
Favg=100000 N
The magnitude of the force that the delivery van exerts on the car is 100000N.
Drop the next question.