- #1
joelio36
- 22
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1. Question
A lift has a object of mass 5kg inside. Find the reaction force of the lift upon the object, and the object's relative weight when:
The lift is descending with an acceleration of 3m/s
The lift is descending with constant speed
The lift is decelerating at a rate if 3m/s (while descending)
2. My attempts and reasoning
I am confused about this question. I understand that on Earth the acceleration due to gravity is 9.8m/s/s, and the gravitational field is 9.8n/kg. So when the lift is at constant speed, acceleration is 0, but their is still an acceleration due to gravity (otherwise the object would lift off floor), so i assume weight & reaction = (9.8 * 5)= 49N
When the lift is descending at 3m/s/s, does this mean total acceleration is 9.8 + 3 = 12.8m/s, so weight and reaction both equal 12.8*5= 64N?
When the lift is retarding at 3m/s/s, total acceleration= 9.8-3= 6.8N, therefore weight and reaction both = 6.8 * 5= 34N.
I have no idea if my logic is right, close, or no where near, since this is what my buddy is doing, I haven't done it yet, because we are in different classes. are my answers right, if not, why?
PS- does anyone know a good website to help explain physics concepts at a-level/K10-12, undergrad level?
A lift has a object of mass 5kg inside. Find the reaction force of the lift upon the object, and the object's relative weight when:
The lift is descending with an acceleration of 3m/s
The lift is descending with constant speed
The lift is decelerating at a rate if 3m/s (while descending)
2. My attempts and reasoning
I am confused about this question. I understand that on Earth the acceleration due to gravity is 9.8m/s/s, and the gravitational field is 9.8n/kg. So when the lift is at constant speed, acceleration is 0, but their is still an acceleration due to gravity (otherwise the object would lift off floor), so i assume weight & reaction = (9.8 * 5)= 49N
When the lift is descending at 3m/s/s, does this mean total acceleration is 9.8 + 3 = 12.8m/s, so weight and reaction both equal 12.8*5= 64N?
When the lift is retarding at 3m/s/s, total acceleration= 9.8-3= 6.8N, therefore weight and reaction both = 6.8 * 5= 34N.
I have no idea if my logic is right, close, or no where near, since this is what my buddy is doing, I haven't done it yet, because we are in different classes. are my answers right, if not, why?
PS- does anyone know a good website to help explain physics concepts at a-level/K10-12, undergrad level?