# The time that it will take to travel 300 ft. if the initial velocity is 20ft/second and final velocity is 60ft/second.

lemjay | High School Teacher | (Level 3) Senior Educator

Posted on

Since the velocity is not constant, solve for the average velocity.

`bar(v)=(v_f+v_i)/2`

`bar(v)=(60+20)/2=80/2=40`

Then, apply the formula:

`bar(v)=d/t`

where d - displacement and t - total time.

So,

`40=300/t`

`40t=300`

`t=300/40`

`t=7.5`

Hence, it took 7.5 seconds to travel 300ft with the given velocities.

oldnick | (Level 1) Valedictorian

Posted on

the equation of motion are:

`s=s_0+at`    and :  `T=T_0+s_0t +1/2 at^2`

where s is speed, a acceleration and T the space.

(`s_0` and`T_0`  are the initial speed and the initial sapce forom a system of  coordinates. We further supposed the uniformly accelerated motion with a=costant)

so we have:

`at= s-s_0`  (1)

`T-T_0=s_0t+1/2at^2`   (2)

We know both value   `s-s_0= 60-20=40`  than `T-T_0=300`

that is:  `at=40`   (3)

Substituing this in (2):

`T-T_0= s_0t+ 20t`

thus:

`300=20t+20t=40t`     `t= 7,5sec`