Newton's Laws Of motion Please Reply

In summary, if the window washer pulls with an addition 9% of force then the upward force will be 70 \times 9.8 \times 1.09 = 747.74N.
  • #1
chazgurl4life
52
0
This is my problem:

A window washer pulls herself upward using the bucket-pulley apparatus The mass of the person plus the bucket is 70 kg.

A) How hard must she pull downward to raise herself slowly at constant speed?...N
(b) If she increases this force by 9%, what will her acceleration be?
.....m/s2

I figured out part A) by taking 70 kg and multiplying it by 1/2 A which equals 4.9m/s2 and so the answer is 343 Newtons. But for part b i am confused as to how to use the the 9% and how to work it out..
 
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  • #2
Well what is 9% of 343? And what does an unbalanced force create?
 
  • #3
9 percent of 343 is 30.47 N ..so if her new force net equal 374 N where should i go from there?.. I am sorry i just been working on this problem for a while and I am still stuck
 
  • #4
Ok, so what is the net force acting on her and the bucket?
 
  • #5
isnt the net force =343+/-30.97?
 
  • #6
No. I mean the resultant force.
 
  • #7
Think about what force is pulling the bucket and the girl down and what force is pulling them up.
 
  • #8
the force pulling on the bucket and the girl is mg= mass x gravity (9.8 m/s2)...the normal force-the force she is pulling the pulley down is the only other force i can think of
 
  • #9
Hang on a minute, why did you half the acceleration due to gravity?
Downwards force = [itex] 70 \times -9.8 = -686N [/itex].
Therefore, the girl must be pulling 'up' with [itex] 686N [/itex] to travel at a constant speed. However, if she pulls with an addition 9% of force then the upward force will be [itex] 70 \times 9.8 \times 1.09 = 747.74N [/itex].
This means there is an unbalanced force of [itex] 747.74-686 = 51.74N [/itex]. Using [itex] F = ma \Rightarrow a = \frac{F}{m} = \frac{51.74}{70} = 0.739 m\cdot s^{-2}[/itex]
 
Last edited:
  • #10
i was confused on this same problem but i don't understand where the 1.09 comes from...?
 
  • #11
1.09*x will give you the sum of the value of x plus 9% (0.09) of x

(instead of doing 9% of x, then adding to x)
 
  • #12
ok i got it thanks so much!
 

Related to Newton's Laws Of motion Please Reply

What are Newton's three laws of motion?

Newton's three laws of motion are the basic principles of physics that describe how objects move. The first law, also known as the law of inertia, states that an object at rest will stay at rest and an object in motion will stay in motion with a constant velocity unless acted upon by an external force. The second law states that the force applied to an object is equal to its mass times its acceleration. The third law states that for every action, there is an equal and opposite reaction.

How do Newton's laws apply to everyday life?

Newton's laws of motion apply to everyday life in many ways. For example, the first law explains why objects stay in motion until acted upon by an outside force, like a ball rolling down a hill. The second law explains how much force is needed to accelerate an object, such as pushing a shopping cart. The third law explains why we feel a force when we push against a wall or when a rocket launches.

What is the difference between mass and weight according to Newton's laws?

Mass and weight are often used interchangeably, but they have different meanings according to Newton's laws of motion. Mass is a measure of the amount of matter in an object and remains constant regardless of an object's location. Weight, on the other hand, is a measure of the force of gravity on an object and can change depending on an object's location. For example, an object will have the same mass on Earth and on the moon, but its weight will be different due to the different gravitational forces.

Can Newton's laws be broken or modified?

Newton's laws of motion have been tested and proven to be accurate in countless experiments. However, they are not absolute and can be modified or expanded upon in certain situations, such as when dealing with objects traveling at speeds close to the speed of light or in the context of quantum mechanics. Additionally, other forces such as friction and air resistance can affect an object's motion and may need to be considered when applying Newton's laws.

How did Newton's laws contribute to the development of modern physics?

Newton's laws of motion were a crucial foundation for the development of modern physics. They provided a framework for understanding and predicting the motion of objects, which was essential for advancements in fields such as engineering, astronomy, and mechanics. Newton's laws also paved the way for further scientific discoveries and theories, such as Einstein's theory of relativity.

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