1. Which of the following statements is true about a system of two particles? Ex
ID: 1974904 • Letter: 1
Question
1. Which of the following statements is true about a system of two particles? Explain your answer.a) it is possible for the system to have net zero momentum, but a net non-zero kinetic energy
b) it is possible for the system to have net zero kinetic energy, but a net non-zero momentum
c) Both a and b are possible
d) neither a nor b are possible
2. A car of mass m and speed v has a head-on collision with a truck of mass 2m and speed v/2. Which has the greater momentum change? Explain your answer. a) the car
b) the truck
c) both have the same momentum change
d) it is impossible to say without knowing the velocities after the collision
3. A railroad car with an open top travels with constant speed. Suddenly, it starts to rain and rain falls into the cart, straight down. What happens to the speed of the cart? Explain your answer
4. You are driving down a narrow street surrounded on both sides by a concrete wall. Suddenly, you see someone driving in the opposite direction, toward you, in an identical car at the same speed. You also realize with alarm that your brakes have failed. You have two choices: swerve into the solid concrete wall, or continue straight and collide with the on-coming identical car. What should you do if your objective is to minimize harm to yourself? Explain your answer.
a) swerve into the wall
b) continue straight into the car
c) it doesn't matter - either choice results in about the same amount of harm
Explanation / Answer
1-a because momentum is vector and k.e is scalar 2)-d data insufficient to conclude anything ( we need one final velocity) 3)since horizontal momentum must be conserved mv=(m+M)V V=m/(m+M)*v so velocity decreases 4)when two bodies of equal mass collide their velocities are exchanged so hitting the car would push the car in the opposite direction with velocity v hence impulse =2mv but hitting the wall the car will stop so impulse = mv hence swerve into the wall
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