A body with an initial velocity of -8 m/s moves with a constant acceleration of -4 m/s² and travels 640 m in 40 seconds. What is its final velocity?

16m/s

Explanation:  u=8m/s, t=40s, d=640m . so by the formula s= ut+1/2at^2 we will find acceleration . 640= 8×40+1/2×a×40×40= 640-320= 800a . 320/800=a. therefore a= 0.4m/s^2 . then find final velocity. v= u +at. v= 8+0.4×40 .v=24m/s. then average velocity = 640/40 =16m/s.

72m/s

Explanation:

Since we're given:

u = 8m/s, a = 4m/s², s = 640m, t = 40

we are going to use the formula:

v² = u² + 2as

Let's substitute with the values

v² = 8² + 2 × 4 × 640

v² = 64 + 5120

v² = 5184

v = 72m/s

conduction, convection, radiation