3. A car waits at a red light for a few seconds, and then accelerates straight ahead to 54 km/h in 3.1 s and then cruises at a constant speed for 75 m. The road is straight. Find the total
distance and time travelled

In the first 3.1 s, the car accelerates with acceleration a from rest to a speed of 54 km/h = 15 m/s, so its acceleration is

15 m/s = a (3.1 s)

a = (15 m/s) / (3.1 s)

a ≈ 4.8 m/s²

So in this time, it travels a distance of

x = 1/2 (4.8 m/s²) (3.1 s)²

x = 23.25 m

For the remaining time, it moves at a constant 15 m/s, covering a distance x of

x = (15 m/s) t

for until it moves 75 m, which takes

75 m = (15 m/s) t

t = (75 m) / (15 m/s)

t = 5 s

So, the car travels a total distance of 98.25 m in 8.1 s.

we need answer choices

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.