Question

a cyclist is travelling at 15 m/s. She applies brakes so that she does not collide with a wall 18m away. What deceleration must she have?

Answer 1

Hey dear here is your answer!!!!!!

u= 15m/s
v= 0
a= ?
s= 18m

From 3rd equation of motion;
$v ^{2} - u ^{2} = 2as$
Substitute the values ....

0-225= 2× a× 18
-225/36= a
a= -6.25

Therefore it must have 6.25 deacceleration ....

Hope it helps u dear....☺️☺️☺️☺️

Answer 2

here final velocity will become 0
and acceleration =?
distance =18m
using equation
$v {}^{2} - u {}^{2} = 2as$
v=0

-u^2=2a×18
-225=2×a×18
-75=2×a×6
a=-75÷12
a=-25/4
a=-6.25m/s^2