Question

please solve part 3 (no spam please)​

Answer 1

Retardation starts after 20 seconds.

Velocity becomes 0 after 30 seconds.

Therefore,

v = 0 m/s

u = 30 m/s

t = (30 - 20)s = 10 seconds

Henceforth,

acceleration ,

$\Large{ \longmapsto a = \frac{v - u}{t} }$

$\Large{ \Rightarrow a = \frac{(0 - 30) \: m/s}{10 \: s} }$

$\Large{ \Rightarrow a = \frac{ - 30 \: }{10 \: } m/ {s}^{2} }$

$\Large{ \Rightarrow a = \frac{ - 3 \cancel{0} \: }{1 \cancel{0} \: } m/ {s}^{2} }$

$\Large{ \Rightarrow a = - 3 \: m/ {s}^{2} }$

There is negative ( - ) sign because the acceleration is in opposite direction, i.e.: RETARDATION.

Answer:

Retardation $= - 3 \: m/ {s}^{2}$

Answer 2

Answer:

At time interval 20-30

Explanation:

When a body is retarding, the velocity of body decreases

Here, we can see that velocity is decreasing in the time interval 20-30 by the given values

So, The body is retarding in the time interval 20-30