If the runner ends where she started, then her total displacement is 
, which means her average velocity will be
The total distance she traversed, however, was 
, which gives her an average speed of
1.t
2.f
3.f
4.t
5.t
6.t
7.f
8.f
9.t
10.t
11.f
12.t
13.t
14.f
15.t
16.f
17.t
18.t
19.f
20.t
21.f
22.t
23.f
24t
22.5 m/s
This is because the puck will not slow down, and maintain a constant velocity.
Answer:
80%
Explanation:
Efficiency of machine = work output/work input ×100 %
From question, work output = 20J
Work input = 25J.
Therefore efficiency = 20/25 × 100 %
Efficiency = 20×4 %
Efficiency = 80%
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Average speed = (total distance) / (total time)
Total distance = (70km + 104km + 79km) = 253 km
Total time = (2hr + 1.5hr + 2hr) = 5.5 hrs
Average speed = (253 km) / (5.5 hrs)
<em>Average speed = 46 km/hr</em>
