Answer:
49.8 km/h
Explanation:
We can determine the average speed by calculating the total distance covered and the time taken,
- First part of the trip:
v1 = 95.0 km/h = 26.4 m/s
t1 = 25.0 min = 1500 s
Distance covered:
[tex]d_1 = v_1 t_1 = (26.4 m/s)(1500 s)= 39600 m = 39.6 km[/tex]
- Second part of the trip:
v2 = 100.0 km/h = 27.8 m/s
t2 = 16.0 min = 960 s
Distance covered:
[tex]d_2 = v_2 t_2 = (27.8 m/s)(960 s)=26688 m= 26.7 km [/tex]
- Third part of the trip:
v3 = 40.0 km/h = 11.1 m/s
t3 = 50.0 min = 3000 s
Distance covered:
[tex]d_3 = v_3 t_3 = (11.1 m/s)(3000 s)=33300 m = 33.3 km [/tex]
The person also spend 30.0 min without moving:
t4 = 30.0 min = 1800 s
Total distance covered:
[tex]d=d_1 +d_2 +d_3 = 39.6 km +26.7 km + 33.3 km =99.6 km[/tex]
Total time taken:
[tex]t=t_1 +t_2 +t_3+t_4 = 1500 s+ 960 s+ 3000 s+1800 s=7260 s = 2.0 h[/tex]
So, the average speed is
[tex]v=\frac{d}{t}=\frac{99.6 km}{2.0 h}=49.8 km/h[/tex]
