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# Mechanics (M1) watch

1. if you've got someone in a lift, and theyre holding a briefcase and the lift is accelerating, do you resolve the briefcase and hand, and man and lift separately?

also, what 3 forces would be relating to the man - i count two, myself; weight and normal reaction?
2. (Original post by kikzen)
if you've got someone in a lift, and theyre holding a briefcase and the lift is accelerating, do you resolve the briefcase and hand, and man and lift separately?

also, what 3 forces would be relating to the man - i count two, myself; weight and normal reaction?
You wouldnt have to resolve the briefcase i dont think, not for M1 at least.

I did M1 last year and Ive forgotten all of it lol even though i did well, so I might be wrong but:

Youve got the normal reaction, the weight of the man and the force pushing the man upwards (the lift motor). Thats if the lift is going upwards.
3. (Original post by kikzen)
if you've got someone in a lift, and theyre holding a briefcase and the lift is accelerating, do you resolve the briefcase and hand, and man and lift separately?

also, what 3 forces would be relating to the man - i count two, myself; weight and normal reaction?
nope, dont resolve separately. and the reaction forces are all correct
4. but then wouldnt you get two unknowns?

S (briefcase + hand)
R (man and floor)

[accelerating downwards]

8g + 70g - S - R = 78a
5. (Original post by kikzen)
but then wouldnt you get two unknowns?

S (briefcase + hand)
R (man and floor)

[accelerating downwards]

8g + 70g - S - R = 78a
I really dont know. I fluked the exam and got away with it ...
6. well, thanks anyway :]
7. What does the question want? You don't really need two reactions do you (unless you're doing a ladder problem - M2)?
8. (Original post by kikzen)
if you've got someone in a lift, and theyre holding a briefcase and the lift is accelerating, do you resolve the briefcase and hand, and man and lift separately?

also, what 3 forces would be relating to the man - i count two, myself; weight and normal reaction?
The three forces on the man: Weight, Normal Reaction and the weight of the briefcase.
9. acceleration of the lift = Σforces/Σmasses...i think...if you are drawing diagrams of the forces draw 2:
1. the forces JUST acting on the man inside the lift.
2. the forces acting on the lift taking the mass of the lift really to be the mass of the lift and everything in it.
10. A horizontal force P holds body mass-10kg on a plane which is 30 degrees to the horizontal .
Find the magnitude of P and the normal reaction between the particle and plane..

just wanna confirm that p=5.66?
11. ?
12. (Original post by MIZZ)
A horizontal force P holds body mass-10kg on a plane which is 30 degrees to the horizontal .
Find the magnitude of P and the normal reaction between the particle and plane..

just wanna confirm that p=5.66?
don't you mean 56.6N? (assuming no friction).

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