It took Jack 2 hours to paddle 6.4 km upstream on the Black River to the giant's castle. The speed of the river is 1.8 km/h. How
1 answer:
To find the time Jack takes to cross Swan Lake, his average speed is required:
The time it will take Jack to cross Swam Lake is <u>0.5 hours</u>
Reason:
Time it took Jack to paddle 6.4 km upstream, t = 2 hours
Distance Jack paddled, d = 6.4 km
The given speed of the Black River, <em>v₂</em> = 1.8 km/h
The width of the lake, w = 2.5 km
The time it will take Jack to cross Swan Lake
Let <em>v₁</em>, represents Jack's speed, we have;
Therefore;
v₁ = 3.2 + 1.8 = 5
- Jack's speed, v₁ = 5 km/h
The time it will take Jack to cross Swan Lake, = <u>0.5 hours</u>
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Answer:
Step-by-step explanation:
Power is defined by work over time. In physics, work can be defined as the energy transferred over from an applied force over some distance. As a formula:
, where F = force applied and d = distance that force is applied over.
*It is worth noting that F must be parallel to the distance travelled. If it is perpendicular, no work is done, and if it is at an angle, find the parallel component and use that for F.
In this case, the force applied must counter the force of gravity on Martha, which is given by , where m = Martha's mass and g = gravitational constant 9.8 m/s/s. Therefore,
. Since she raises her body 4.0 meters, the work done must be
.
Since power is equal to work over time and t = 2.3 seconds, we have:
(to two significant figures)