The diagram below shows a person using a device called a jetpack. Water is forced downwards from the jetpack and produces an upw
ard force on the person. State the condition necessary for the person to be able to remain stationary in mid-air.
1 answer:
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Answer:
Length of copper wire, l = 785 meters
Explanation:
Given that,
Resistance of the copper wire, R = 0.172 ohms
Area of cross section,
Resistivity of copper,
The resistance of a wire is given by :
l = 785 meters
So, the length of the copper wire is 785 meters. Hence, this is the required solution.
Answer:
The true statement is:
"(C) The magnitude of the average velocity is equal to 30 m.p.h."
Explanation:
Given that a car travels 30 miles in 1 hour on a winding mountain road.
Let' check all the statements one by one:
(A) The magnitude of the total displacement is larger than the distance traveled.
Since the entire motion of the car is not exactly given in the question, so it is not possible to tell whether the magnitude of the total displacement is larger than the distance traveled or not.
Thus, this statement is not true.
(B) The magnitude of the average velocity is greater than 30 m.p.h.
The average velocity of an object is defined as the total displacement covered by the particle divided by the total time taken in covering that displacement.
Total distance covered by the car = 30 miles.
Total time taken by the car to cover this distance = 1 hour.
Therefore, the average velocity of the car for this time interval =
Thus, this statement is also not true.
(C) The magnitude of the average velocity is equal to 30 m.p.h.
As is cleared in part (B) section above, the average velocity of the car in the given time interval is 30 m.p.h.
Thus, this statement is true.
(D)The magnitude of the average velocity is less than to 30 m.p.h.
Since. the average velocity of the car is 30 m.p.h.
Thus, this statement is not true.
(E)The car traveled with a constant speed of 30 m.p.h.
The motion of the car on the mountain road is not thoroughly given in the question, so again it is not possible to tell whether the car traveled with a constant speed of 30 m.p.h. or not.
Thus, this statement is also not true.
Answer:
(A) 374.4 J
(B) -332.8 J
(C) 0 J
(D) 41.6 J
(E) 351.8 J
Explanation:
weight of carton (w) = 128 N
angle of inclination (θ) = 30 degrees
force (f) = 72 N
distance (s) = 5.2 m
(A) calculate the work done by the rope
- work done = force x distance x cos θ
- since the rope is parallel to the ramp the angle between the rope and
the ramp θ will be 0
work done = 72 x 5.2 x cos 0
work done by the rope = 374.4 J
(B) calculate the work done by gravity
- the work done by gravity = weight of carton x distance x cos θ
- The weight of the carton = force exerted by the mass of the carton = m x g
- the angle between the force exerted by the weight of the carton and the ramp is 120 degrees.
work done by gravity = 128 x 5.2 x cos 120
work done by gravity = -332.8 J
(C) find the work done by the normal force acting on the ramp
- work done by the normal force = force x distance x cos θ
- the angle between the normal force and the ramp is 90 degrees
work done by the normal force = Fn x distance x cos θ
work done by the normal force = Fn x 5.2 x cos 90
work done by the normal force = Fn x 5.2 x 0
work done by the normal force = 0 J
(D) what is the net work done ?
- The net work done is the addition of the work done by the rope, gravitational force and the normal force
net work done = 374.4 - 332.8 + 0 = 41.6 J
(E) what is the work done by the rope when it is inclined at 50 degrees to the horizontal
- work done by the rope= force x distance x cos θ
- the angle of inclination will be 50 - 30 = 20 degrees, this is because the ramp is inclined at 30 degrees to the horizontal and the rope is inclined at 50 degrees to the horizontal and it is the angle of inclination of the rope with respect to the ramp we require to get the work done by the rope in pulling the carton on the ramp
work done = 72 x 5.2 x cos 20
work done = 351.8 J
