Question

The bus is initially traveling at the velocity of 70km/h. Then breakes are applied then it's velocity decreased to 50km/h. If the declarationis 2m/s×s. Calculate the time

Answer 1

Solution :

✴ Given :-

• Initial velocity of bus = 70kmph
• Final velocity of bus = 50kmph
• Acceleration = 2m/s$^2$

✴ To Find :-

• Time interval

✴ Concept :-

▪ Acceleration is defined as ratio of change in velocity to the time interval.

▪ Acceleration is vector quantity.

▪ Acceleration can be positive, negative and zero.

✴ Conversation :-

✒ 1kmph = 5/18mps

✒ 70kmph = 19.44mps

✒ 50kmph = 13.89mps

✴ Calculation :-

$\dashrightarrow\sf\:a=\dfrac{v-u}{t}\\ \\ \dashrightarrow\sf\:(-2)=\dfrac{13.89-19.44}{t}\\ \\ \dashrightarrow\sf\:t=\dfrac{-5.55}{-2}\\ \\ \dashrightarrow\:\boxed{\sf{\pink{\large{t=2.78\:s}}}}$

❄ Negative sign of acceleration shows retardation.