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Answer:
1.2 m from the left end
Explanation:
= mass of the person = 90 kg
= mass of friend = 60 kg
= distance of pivot from the person or from the left end
= length of the seesaw board = 3.0 m
= distance of pivot from the friend or from right end = L - r = 3 - r
Using equilibrium of torque about the pivot

Answer:
Not the right answer in the options, speed is 4.47 m/s, and the procedure is coherent with option A
Explanation:
Answer A uses mass and velocity units, which are momentum units. By using the conservation of momentum:
.
Since Tom stays in the raft, then both are moving with the same speed. From the options, the momentum is in agreement with option A, however, the question asks for speed.
Answer:
4.198 seconds
Explanation:
The total length of the yacht is 30m and the width of the bridge is 14.5m.
The speed of the yacht is 10.6m/s.
We can assume the current of the canal has a speed of 0m/s.
To calculate the answer we will break it into two parts
1) The time it takes for the bow to travel from the start of the bridge to the end
<em>Formula Speed = Distance / Time</em>
Speed = 10.6m/s
Distance = 30m
Time = T1
T1 = 2.8301s
2) The time it takes for the stern to cross the end of the bridge after the bow
<em />
<em>Formula Speed = Distance / Time</em>
<em />
Speed = 10.6m/s
Distance = 14.5m
Time = T2
T2 = 1.3679s
3) The Total Time is
Total = T1 + T2
Total = 4.198s
I believe the best option to go with will be option C. electrons are negatively charged