Helicopter Lifting off(Newtons Laws). Help please?

In summary, to determine the upward force needed for a 7000 lb medical helicopter to lift off at a rate of 10 ft/sec squared, you must add the acceleration of 10 ft/sec to the gravitational acceleration of 32.2 ft/sec squared. This results in an upward force of 4826.1 lbs. The negative sign was incorrect as the 10 ft/sec acceleration is in the opposite direction from gravitational acceleration.
  • #1
bob24
14
0

Homework Statement


A medical helicopter weighs 7000 lbs. How much upward force must the propeller supply for it to lift off at 10ft/sec(squared)?


Homework Equations



T-w=ma, w=mg

The Attempt at a Solution


Here is what I tried:
T-w=ma.....w=mg---7000=m(32.2)=217.39k
T-7000= 217.39(-10ft/s)
T=4826.1

What am I doing wrong here? Shouldnt the acceleration be a negative value since it is going upward? and what should the actual final answer be?
 
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  • #2
F = m * a

now, to go up, it must counter both gravitational acceleration, plus add that additional 10 ft/sec acceleration

so "a" = 10 ft/sec + ...
 
  • #3
I see, thank you.
So technically, the only thing I did wrong was the negative sign.
 
  • #4
Yeah, because if you're doing T-w then you're saying that 'g' is acting in the negative direction since you're subtracting it from upward force. Since the 10 ft/s are in the opposite direction from g, it can't be negative TOO
 

FAQ: Helicopter Lifting off(Newtons Laws). Help please?

1. How does a helicopter take off and stay in the air?

A helicopter uses the principle of lift, which is governed by Newton's Third Law of Motion. The rotor blades of a helicopter spin at high speeds, creating a difference in air pressure above and below the blades. This difference in pressure allows the helicopter to lift off the ground and stay in the air.

2. What is Newton's Third Law of Motion and how does it apply to a helicopter's takeoff?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. In the case of a helicopter, the action is the downward force generated by the spinning rotor blades, and the reaction is the upward force that propels the helicopter off the ground.

3. Can a helicopter take off in any direction?

Yes, a helicopter can take off in any direction because of the ability to maneuver its rotor blades. By tilting the blades in different directions, a helicopter can move forward, backward, left, or right.

4. How does the weight of the helicopter affect its takeoff?

The weight of a helicopter affects its takeoff by requiring more power from the engine to generate enough lift to overcome the force of gravity. Heavier helicopters will need a longer runway or more powerful engines to lift off the ground.

5. Are there any other factors besides Newton's Laws that affect a helicopter's takeoff?

Yes, there are other factors that can affect a helicopter's takeoff, such as air density, wind speed and direction, and the weight and distribution of cargo or passengers on board. These factors can impact the lift and stability of the helicopter during takeoff.

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