Calculating Force Needed to Lift 79kg Mass at Const. Speed

In summary, a woman weighing 79 kg raises herself in a bucket by pulling with a force of 774.2 N, which is enough to overcome the gravitational force of 774.2 N. The net force must be 0 for her to raise at a constant speed, and the method used to raise herself is not specified.
  • #1
daltomagne
4
0
A woman raises herself in a bucket. How hard must she pull downward to raise herself slowly at constant speed? The mass of the person plus the bucket is 79 kg.

m=79kg
g=9.8m/s^2 (downward)

i know [tex]\Sigma[/tex]F=ma so i end up with 774.2 N. I'm a little lost as where to go now.
 
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  • #2
Sum the forces in the y direction, if speed is constant that acceleration is zero

Forces in y =Fp- Fg = 0

Solve for fp
 
  • #3
You actually already solved it. For something to move at a constant speed, the net force has to be 0. So she just has to pull hard enough to overcome the gravitational force. Which you already calculated.
 
  • #4
You need to understand how she is raising herself. A simple rope and pulley arrangement? A diagram would be helpful.
 
  • #5


I would first like to commend you for using the correct formula, ΣF=ma, to calculate the force needed to lift the 79kg mass at a constant speed. Your calculation of 774.2 N is correct.

To answer the question of how hard the woman must pull downward to raise herself slowly at constant speed, we need to consider the forces acting on the system. In this case, the only forces present are the gravitational force (weight) of the woman and the bucket, and the force exerted by the woman pulling on the bucket.

Since the woman is raising herself at a constant speed, we can assume that the net force acting on the system is zero, as there is no acceleration. This means that the force she exerts by pulling down on the bucket must be equal in magnitude to the weight of the system, which is 774.2 N.

In other words, the woman must pull down with a force of 774.2 N to counteract the weight of the system and raise herself at a constant speed. This is because the two forces are in equilibrium, resulting in a net force of zero.

It is important to note that this calculation assumes ideal conditions, such as a frictionless pulley system and no other external forces acting on the system. In reality, there may be other factors that could affect the force needed, such as the friction between the bucket and the pulley or the strength and technique of the woman pulling on the bucket.

In conclusion, the force needed for the woman to raise herself slowly at a constant speed is 774.2 N, which is equal in magnitude to the weight of the system. This is due to the equilibrium of forces in this scenario.
 

Related to Calculating Force Needed to Lift 79kg Mass at Const. Speed

1. How do you calculate the force needed to lift a 79kg mass at a constant speed?

To calculate the force needed to lift a 79kg mass at a constant speed, you can use the formula F = m x g, where F is the force in Newtons, m is the mass in kilograms, and g is the acceleration due to gravity (9.8 m/s^2). In this case, the force needed would be 79kg x 9.8 m/s^2 = 774.2 N.

2. Why is it important to consider the mass and constant speed when calculating force?

The mass and constant speed are important factors to consider when calculating force because they directly affect the amount of force needed. A heavier mass will require more force to lift, and a constant speed means that the force needs to not only lift the mass but also counteract any opposing forces, such as friction or air resistance.

3. Can the force needed to lift a 79kg mass at a constant speed change?

Yes, the force needed to lift a 79kg mass at a constant speed can change depending on the environment and any external forces acting on the mass. For example, if there is an increase in friction or air resistance, more force will be needed to maintain the constant speed.

4. How does the angle of the lift affect the force needed to lift a 79kg mass at a constant speed?

The angle of the lift can affect the force needed to lift a 79kg mass at a constant speed because it changes the direction of the force. If the lift is at an angle, the force needed will be greater to compensate for the vertical and horizontal components of the force.

5. What other factors may influence the force needed to lift a 79kg mass at a constant speed?

Other factors that may influence the force needed to lift a 79kg mass at a constant speed include the strength and angle of the lifting mechanism, the condition of the surface the mass is being lifted on, and any external forces acting on the mass such as wind or vibrations.

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