Answer:
10 km/hr/s
Explanation:
The acceleration of an object is given by

where
v is the final velocity
u is the initial velocity
t is the time
For the car in this problem:
u = 0

t = 6 s
Substituting in the equation,

Answer:
410 m
Explanation:
Given:
v₀ = 20.5 m/s
a = 0 m/s²
t = 20 s
Find: Δx
Δx = v₀ t + ½ at²
Δx = (20.5 m/s) (20 s) + ½ (0 m/s²) (20 s)²
Δx = 410 m
The correct answer is:
Work is negative, the environment did work on the object, and the energy of the system decreases.
In fact, the work-energy theorem states that the work done by the system is equal to its variation of kinetic energy:

In this problem, the variation of kinetic energy
is negative (because the final velocity is less than the initial velocity), so the work is negative, and this means that the environment did work on the object, and its energy decreased.