Physics Jamb, Waec, Neco Past Questions & Answers on Speed, Velocity and Acceleration

 QUESTIONS 20. A motor vehicle is brought to rest from a speed of 15m/s in 20 seconds. Calculate the retardation. 

A. 0.75ms'2 B. 1.33ms'2 C. 5.00ms'2 D. 7.50ms'2 JAMB 1994 Ans:0.75m/s2

Solutions 

Initial velocity u = 15m/s

Final velocity v = 0m/s

Time t = 20s

Acceleration or retardation a = ?

Using the first equation of motion 

v = u + at

0 = 15 + a (20)

0-15 = 20a

-15/20= -a ( because retardation is the negative of acceleration)

-0.75 = -a =>>>> multiply through by - negative sign

a = 0.75m/s²