When a brick is dropped from the roof of a house, it lands on the ground with a speed v. What will the speed at ground level be
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A 10-kg cart moving at 5 m/s collides with a 5-kg cart at rest and causes it to move 10 m/s. Which principle explains the result? A) law of differential mass B) law of conservation of momentum C) law of unequal forces D) law of accelerated collision
We have the following data¹:
ΔP (momentum before impact) = ?
mA (mass) = 10 kg
vA (velocity) = 5 m/s
mB (mass) = 5 kg
vB (velocity) = 0 m/s
Solving:
ΔP = mA*vA + mB*vB
ΔP = 10 kg*5 m/s + 5 kg*0 m/s
ΔP = 50 kg*m/s + 0 kg*m/s
Δp = 50 kg*m/s ← (momentum before impact)
We have the following data²:
ΔP (momentum after impact) = ?
mA (mass) = 10 kg
vA (velocity) = 0 m/s
mB (mass) = 5 kg
vB (velocity) = 10 m/s
Solving:
Δp = mA*vA + mB*vB
Δp = 10 kg*0 m/s + 5 kg*10 m/s
Δp = 0 kg*m/s + 50 kg*m/s
Δp = 50 kg*m/s ← (momentum after impact)
*** Then, which principle explains the result ?
Law of conservation of momentum, <u>since the total momentum of body A and B before impact is equal to the total momentum of body A and B after impact.</u>
Note: Bodies of different masses and velocities may have the same kinetic energy, if proportionality between the units is maintained it can occur that they have the same kinetic energy.
Answer:
B) law of conservation of momentum
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