Question

A speedboat increases its speed uniformly from 20 m/s to 31 m/s in a distance of 240 m.

a) find the magnitude of its acceleration.
___ m/s^2
b) find the time it takes the boat to travel the 240 m distance.
___ s

Answer 1

A friend sent me this as the answer but I don't quite understand it
240=1/2at^2+V(0)t , V=at+V(0),31=at+20 ,at=11
240=1/2(at)t +20t , 240=5.5t+20t=25.5t,
t=240/25.5=9.41sec
a=11/9.41=1.16875m/sec^2

Answer 2

oh dear It is an easy one..
we have
v=31m/s
u=20m/s
d=240m

so \[v ^{2}-u ^{2}\]=2 a d;

\[31^{2}-20^{2}\]=2xax240;

961-400=2xax240;

561/(2x240)=a

so, 561/480=a

so,a=1.16m/sec^2


and for the 2nd part,

we have,v=u+at
putting the values of v u and a we get t;

31=20+1.16t;
31-20=1.16t;
11/1.16=t
thus we have t=9.48 sec.

Answer 3

Thank you, my teachers say I have a problem with over complicating things.

Answer 4

it was easy isn't it?actually the other guy used the 2nd equation of motion while i used the first and third laws.

Answer 5

i mean equations