Someone explain pls? If a runner decreases his velocity from +20 m/s to +10 m/s, with average acceleration is -5m/s². What was the time taken?

Answer 1

Hey Maria!

We know that acceleration is equal to change in velocity over time, or:

a= Δv/t

Our change in velocity is V_final-V_initial, which is 10m/s-20m/s= -10m/s

Rearranging this equation to solve for time, we get that

t= Δv/a

Plugging in our values for velocity and acceleration, we get:

t= -10m/s/-5m/s²

t= 2s

Hope this helps!

Answer 2

2 seconds

in one second the runner goes from 20 to 15, in 2 seconds down to 10 m/s

acceleration of -5m/sec^2 means that every second the velocity decreases by 5 m/s

in 2 seconds the velocity decreases by 2 x 5 = 10 m/s. 20-10 = 10m/s