A 7.0kg skydiver is descending with a constant velocity
1 answer:
Answer:
Air resistance: 68.6 N
Explanation:
For the skydiver falling down, there are two forces acting on him:
- The force of gravity, of magnitude
where
m = 7.0 kg is the mass of the skydiver
is the acceleration of gravity
This force acts in the downward direction
- The air resistance, R, in the upward direction
So the net force on the skydiver is:
According to Newton's second law of motion, the net force is also equal to mass times acceleration:
However, in this problem the skydiver is falling at constant velocity, so his acceleration is zero:
Therefore, the net force is zero:
And so we can find the magnitude of the air resistance, which is equal to the weigth of the skydiver:
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<h2>a) Average velocity in first 4 seconds is 64 ft/s upward</h2><h2>b) Average velocity in second 4 seconds is 63.5 ft/s downward</h2>
Explanation:
a) Given S(t) = 76 + 128t − 16t²
s(0) = 76 + 128 x 0 − 16 x 0² = 76 ft
s(4) = 76 + 128 x 4 − 16 x 4² = 332 ft
Displacement in 4 seconds = 332 - 76 = 256 ft
Time = 4 - 0 = 4 s
Average velocity in first 4 seconds is 64 ft/s upward
a) Given S(t) = 76 + 128t − 16t²
s(4) = 76 + 128 x 4 − 16 x 4² = 332 ft
s(8) = 76 + 128 x 8 − 16 x 8² = 78 ft
Displacement in 4 seconds = 78 - 332 = -254 ft
Time = 4 - 0 = 4 s
Average velocity in second 4 seconds is 63.5 ft/s downward
The force needed to accelerate an elevator upward at a rate of is 2000 N or 2 kN.
<u>Explanation: </u>
As per Newton's second law of motion, an object's acceleration is directly proportional to the external unbalanced force acting on it and inversely proportional to the mass of the object.
As the object given here is an elevator with mass 1000 kg and the acceleration is given as , the force needed to accelerate it can be obtained by taking the product of mass and acceleration.
So 2000 N or 2 kN amount of force is needed to accelerate the elevator upward at a rate of .