You understand the concepts all perfectly fine, just have applied them slightly incorrectly.
Firstly, the speed time graph is actually a triangle since the question says a steady acceleration from rest - i.e. it started at 0 and worked up to 2ms-1 in the space of that 10 seconds. The area under the graph is the distance, and a triangle area is found with bh/2, and in this case that is 10*2/2 = 10m - so the boat travelled 10 metres.
Work done as you correctly stated is fd - giving the part against water resistance as 3*10 = 30J
However, you forgot to do the last part - the key words are rate of work - this means Power. Power is Energy/Time, and this whole process occurred over 10 seconds. So whilst 30J of energy were expended due to the water resistance, this didn't all occur in no time. So we need to divide that by 10 to get the power. And 30/10 is 3J/s - and J/s is the same as W.
Answer:
Velocity
Explanation:
Velocity is a vector quantity which is defined as the rate of displacement. Displacement is also a vector quantity which is measured as the shortest distance between the final point form the reference point.
Velocity is negative when the displacement is negative, displacement can be negative if taken in opposite direction form the desired direction with respect to the initial point.
Answer:
Apparent frequency increases for Bob and decreases for Jill.
Explanation:
Doppler effect refers to the apparent change in frequency when there is relative motion between source and the listener. When the source and listener move closer, the apparent frequency heard by the listener increases. And when the source and listener move away from each other, the apparent frequency heard by the listener decreases.
Thus, when the emergency vehicle approaches Bob, the apparent frequency of the siren increases. It moves away from Jill, the apparent frequency heard by the Jill decreases.
I know. If you're asking for ideas, I once did one and it did not break. I just took a cardboard box, filled it with thins like packing peanuts, crumpled newspaper, and put the egg inside a few layers of socks in the middle, and taped the box tightly shut. Our science teacher dropped from the roof of the school, and there wasn't even a crack on mine!
