You stand on a skateboard at rest and throw a rock at 5 m/sec. You move back at 0.5 m/ sec. What is the combined mass of you and the skateboard?

Question

HIX Tutor · Accepted Answer

undefined To find the combined mass of you and the skateboard, first, calculate the change in momentum when you throw the rock and then move backward.
1. Calculate the momentum of the rock: momentum = mass x velocity.
2. Calculate the momentum of you and the skateboard when you move backward: momentum = combined mass x velocity.
3. Since momentum is conserved, the total momentum before and after throwing the rock should be the same.
4. Set up and solve the equation: momentum before = momentum after to find the combined mass.

Nathan Ashcroft · Answer

10 times the mass of the rock

Utilizing momentum conservation, The rock's change in momentum plus yours equals zero. (You mass) × (Velocity change) + (Rock mass) × (Velocity change) = 0 Rock's mass (5 m/s) + your mass (-0.5 m/s) equals 0. Rock's mass = 10 times your mass

Nathan Ashcroft · Answer

undefined The combined mass of you and the skateboard is 10 kg.