A child walks 5.0 meters north, then 4.0 meters east, and finally 2.0 meters south. what is the magnitude of the resultant displ
acement of the child after the entire walk
2 answers:
Answer:
Resultant displacement of the child is 5 m.
Explanation:
It is given that, a child walks 5.0 meters north, then 4.0 meters east, and finally 2.0 meters south.
We have to find the magnitude of displacement of the child after the entire walk. The attached figure shows entire journey of the child. Displacement of an object is equal to the shortest path covered by it. Here, AM shows the net displacement. It can be calculated using Pythagoras theorem as :
Since, AB = 5 m So, OA = 3 m and BC = OM = 4 m
⇒ AM = 5 m
Hence, the resultant displacement of the child after the entire walk is 5 m.
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Answer:
v = 0.41 m/s
Explanation:
- In this case, the change in the mechanical energy, is equal to the work done by the fricition force on the block.
- At any point, the total mechanical energy is the sum of the kinetic energy plus the elastic potential energy.
- So, we can write the following general equation, taking the initial and final values of the energies:
- Since the block and spring start at rest, the change in the kinetic energy is just the final kinetic energy value, Kf.
- ⇒ Kf = 1/2*m*vf² (2)
- The change in the potential energy, can be written as follows:
where k = force constant = 815 N/m
xf = final displacement of the block = 0.01 m (taking as x=0 the position
for the spring at equilibrium)
x₀ = initial displacement of the block = 0.03 m
- Regarding the work done by the force of friction, it can be written as follows:
where μk = coefficient of kinettic friction, Fn = normal force, and Δx =
horizontal displacement.
- Since the surface is horizontal, and no acceleration is present in the vertical direction, the normal force must be equal and opposite to the force due to gravity, Fg:
- Fn = Fg= m*g (5)
- Replacing (5) in (4), and (3) and (4) in (1), and rearranging, we get:
- Replacing by the values of m, k, g, xf and x₀, in (7) and solving for v, we finally get: