Relative velocity is the velocity of one object with respect to another object. It tells how fast and in which direction one object appears to move when observed from another moving object.
If two bodies A and B are moving with velocities vA and vB respectively, then the velocity of A relative to B is:
vAB = vA − vB
If two bodies move in the same direction, relative velocity is the difference of their speeds.
vAB = vA − vB
If two bodies move in opposite directions, relative velocity is the sum of their speeds.
vAB = vA + vB
When velocities are not along the same straight line, relative velocity is obtained using vector subtraction.
Q1. Relative velocity is: A) Scalar quantity B) Vector quantity C) Constant quantity D) Zero quantity Answer: B Q2. Velocity of A relative to B is given by: A) vA + vB B) vB − vA C) vA − vB D) vA × vB Answer: C Q3. Two bodies move in the same direction with speeds 10 m/s and 6 m/s. Find their relative speed. A) 4 m/s B) 6 m/s C) 10 m/s D) 16 m/s Answer: A Q4. Two bodies move in opposite directions with speeds 5 m/s and 7 m/s. Their relative speed is: A) 2 m/s B) 12 m/s C) 35 m/s D) 7 m/s Answer: B Q5. Relative velocity depends on: A) Only speed B) Only direction C) Speed and direction D) Mass Answer: C Q6. If two bodies have the same velocity, their relative velocity is: A) Maximum B) Minimum C) Zero D) Infinite Answer: C Q7. Relative velocity is useful in studying: A) One-dimensional motion only B) Projectile motion only C) Motion of bodies with respect to each other D) Rest condition only Answer: C Q8. Which situation uses relative velocity? A) Free fall B) Circular motion C) Boat in river D) Simple harmonic motion Answer: C
Relative velocity is the velocity of one body with respect to another.
vAB = vA − vB
Relative speed = difference of speeds
Relative speed = sum of speeds
Relative velocity is a vector quantity.
Direct MCQs and numericals are asked on same and opposite direction relative velocity problems.
