Theory question 107
DynamicsThe initial velocity of a particle of mass 0.1 kg is 40 ms−1 in the direction of the unit vector j. The velocity of the particle changed to 30 ms−1 in the direction of the unit vector i. Find the change in momentum.
Show the model answer
Model answer
Initial momentum = 0.1(40j) = 4j; final = 0.1(30i) = 3i.
Change = 3i − 4j (N s).
Magnitude = √(9 + 16) = 5 kg m s⁻¹.
Explanation
Momentum is a vector: subtract the initial from the final.