+0

# Equations of motion

0
210
1

I'm having an issue with two similar questions

1. A particle with uniform acceleration of 4ms-2 and covers 38 m over its fifth second of motion. Using its avarage velocity in this time period find the initial velocity.

2. A body moves with uniform acceleration. It travles 8.5m in the eight second and 7.5 m during the thirteenth second of it's motion. Using the average velocity from this time, find the initial velocity and acceleration.

Acceleration over this time using v=u+at v = 7.5 u = 8.5 t = 5

a = -0.2

Nov 16, 2018

#1
+19697
+2

1.OK.....what is the average velocity?

It covered  38 m     in  0.2 sec

Uh-ohh....your question is unclear in its  wording

in second # 5  did i cover 38 m   or did it cover 38 m in   1/5 sec ????

I will go with the former (though that is not what I initially thought)

vf = vo +  at       =   38 = vo +  (4)(5)

38 = vo +  (20)

18m/s = vo

2. vf = vo + at         =     7.5 = 8.5  + a(5)

-1 = a 5

- .2 = a      OK so we know the accel is negative 0.2  (it is DEccelerating....slowing down)

vf = vo + at

8.5 = vo + (-0.2)(8)

8.5  = vo - 1.6

10.1 m/s = vo

(ALWAYS remember the UNITS)

Nov 17, 2018
edited by ElectricPavlov  Nov 17, 2018