Question

The below figure shows the displacement-time graph of a car. Find the velocity of the car at 15 s and 30 s respectively.

• A. 0 m/s, 0 m/s
• B. 5 m/s, -5 m/s
• C. 10 m/s, -40 m/s
• D. 0m/s, -2.5 m/s

Answer 1

The correct option is D 0m/s, -2.5 m/s

• The graph here shows the motion of the car for a complete 40 seconds.

• We know the slope of the displacement-time graph gives us velocity.

• At 15 s, So here, y2 = 50 m for t2 = 10 s. Similarly, y1 = 0 for t1 = 0 s. Using this, velocity will be

(50-50)/(15-10) = (50/5) = 0 m/s.

• At 30 s, So here, y2 = 0 m for t2 = 40 s. Similarly, y1 = 50 for t1 = 20 s. Using this, velocity will be

(0-50)/(40-20) = -2.5 m/s.