A person exerts a horizontal force of F=45N on the end of an 86cm wide door. The magnitude of the torque due to F about the pivo
t point is determined by |τ|=|rxF|=rFsinθ . Determine the magnitude of the torque, |τ| , on the door about its hinges due to F . |τ|=0Nm |τ|=38.7Nm |τ|=3870Nm
1 answer:
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a) Let's call x the direction parallel to the river and y the direction perpendicular to the river.
Dave's velocity of 4.0 m/s corresponds to the velocity along y (across the river), while 6.0 m/s corresponds to the velocity of the boat along x. Therefore, the drection of Dave's boat is given by:
relative to the direction of the river.
b) The distance Dave has to travel it S=360 m, along the y direction. Since the velocity along y is constant (4.0 m/s), this is a uniform motion, so the time taken to cross the river is given by
c) The boat takes 90 s in total to cross the river. The displacement along the y-direction, during this time, is 360 m. The displacement along the x-direction is
so, Dave's landing point is 540 m downstream.
d) If there were no current, Dave would still take 90 seconds to cross the river, because its velocity on the y-axis (4.0 m/s) does not change, so the problem would be solved exactly as done at point b).
Answer:
5501 kg/m^3
Explanation:
The value of g at the Earth's surface is
where G is the gravitational constant
M is the Earth's mass
is the Earth's radius
Solving the formula for M, we find the value of the Earth's mass:
The Earth's volume is (approximating the Earth to a perfect sphere)
So, the average density of the Earth is