Answer:
Please find attached the Velocity-Time graph, the Displacement-Time graph and the combined Velocity/Displacement-Time graph, created with Microsoft Excel
Explanation:
The given parameters are;
The initial velocity with which the boy throws the rock, u = 12 m/s
The direction in which he throws the rock = Down
The height from which the rock was thrown, h = 20 m
The height at which the river is located = 0 m
The kinematic equation of motion, of the rock can be given as follows;
h = u·t + 1/2·g·t²
Where;
t = The time of motion of the rock
g = The acceleration due to gravity = 9.8 m/s²
h = The height from which the rock is thrown = 20 m
Substituting the known values into given equation, we get;
20 = 12·t + 1/2·9.8·t² = 12·t + 4.9·t²
4.9·t² + 12·t - 20 = 0
t = (-12 ± √(12² - 4×4.9×(-20)))/(2 × 4.9) = (-12 ± √(242))/(9.8)
t ≈ -3.587 seconds or t ≈ 1.138 seconds
Attached please find the Velocity-Time graph, the Displacement-Time graph and the combined Velocity/Displacement-Time graph, created with Microsoft Excel.
Answer:
6.6 N
Explanation:
Let's take the direction of the force of 4.0 N as positive x-direction. This means that the force of 3.0 N is at 40 degrees above it. So the components of the two forces along the x- and y-directions are:
So the resultant has components
So the magnitude of the resultant is
And in order for the body to be balanced, the third force must be equal and opposite (in direction) to this force: so, the magnitude of the third force must be 6.6 N.