Question

a pebble thrown vertically upward with an initial velocity 60m/s comes to a stop in 6 sec. find the retardation​

Answer 1

Understanding the question: This question says that we have to find out the retardation of a pebble which is thrown vertically upward with an initial velocity of 60 metre per second and afterthat it comes to a stop in 6 seconds.

Provided that:

• Initial velocity = 60 m/s
• Time = 6 seconds
• Final velocity = 0 m/s

Don't be confused! Final velocity came as zero because the pebble came at rest of came to stop.

To calculate:

• The retardation

Solution:

• The retardation = +10 m/s²

Using concept:

• Acceleration formula

Using formula:

• ${\sf{a \: = \dfrac{v-u}{t}}}$

Where, a denotes acceleration , v denotes final velocity , u denotes initial velocity and t denotes time taken.

Full Solution:

$:\implies \sf a \: = \dfrac{v-u}{t} \\ \\ :\implies \sf a \: = \dfrac{0-60}{6} \\ \\ :\implies \sf a \: = \dfrac{-60}{6} \\ \\ :\implies \sf a \: = -10 \: ms^{-2} \\ \\ :\implies \sf Acceleration \: = -10 \: ms^{-2} \\ \\ :\implies \sf Retardation \: = +10 \: ms^{-2}$

Don't be confused! Retardation came in positive because acceleration came in negative. And we know that acceleration is the inverse of retardation.