Mechanics- connected particles

In summary: You are correct. In summary, we can solve for the mass of the lift plus its load by using the equation $T - (M_L + 35)g = (M_L + 35)a$ and solving for $M_L$, which gives us a mass of approximately 405 kg. However, if we only want to find the mass of the lift, we can subtract the load (35 kg) from the total mass and get a mass of 370 kg.
  • #1
Shah 72
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A box of mass 20 kg sits on the floor of a lift. A second box of mass 10kg sits on top of the first box and a third box of mass 5kg sits on top of the second box. When the tension in the lift cable is 4260N, the lift is accelerating upwards at 0.5m/s^2.
a) work out the mass of the lift.
b) work out the reaction between the floor of the lift and the first box
c) work out the reaction between the first box and the second box
d) work out the reaction between the second box and the third box.
 
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  • #2
Shah 72 said:
A box of mass 20 kg sits on the floor of a lift. A second box of mass 10kg sits on top of the first box and a third box of mass 5kg sits on top of the second box. When the tension in the lift cable is 4260N, the lift is accelerating upwards at 0.5m/s^2.
a) work out the mass of the lift.
b) work out the reaction between the floor of the lift and the first box
c) work out the reaction between the first box and the second box
d) work out the reaction between the second box and the third box.
I have tried to solve this but not getting the right answers
 
  • #3
a) $T - (M_L + 35)g = (M_L + 35)a$

b) $R_1 - 35g = 35a$

c) $R_2 - 15g = 15a$

d) $R_3 - 5g = 5a$
 
  • #4
skeeter said:
a) $T - (M_L + 35)g = (M_L + 35)a$

b) $R_1 - 35g = 35a$

c) $R_2 - 15g = 15a$

d) $R_3 - 5g = 5a$
Thank you so so much! I will try
 
  • #5
skeeter said:
a) $T - (M_L + 35)g = (M_L + 35)a$

b) $R_1 - 35g = 35a$

c) $R_2 - 15g = 15a$

d) $R_3 - 5g = 5a$
I tried the same earlier but getting the wrong. The textbook ans is 405 kg.
4260- 10m- 350= 0.5m+17.5
 
  • #6
$\dfrac{4260}{10.5} \approx 405$

mass of the lift + 35kg = 405kg (actually, 406 using correct rounding)

the question should be “what is the mass of the lift plus its load”

mass of the lift alone is 370kg
 
  • #7
skeeter said:
$\dfrac{4260}{10.5} \approx 405$

mass of the lift + 35kg = 405kg (actually, 406 using correct rounding)

the question should be “what is the mass of the lift plus its load”

mass of the lift alone is 370kg
Thank you very much!
 

FAQ: Mechanics- connected particles

1. What is the definition of "connected particles" in mechanics?

In mechanics, connected particles refer to a system of particles that are physically linked or connected to each other. This can include objects that are connected by ropes, strings, or other rigid links.

2. How do you calculate the acceleration of connected particles?

To calculate the acceleration of connected particles, you must first determine the net force acting on the system. Then, use Newton's second law (F=ma) to find the acceleration of the center of mass of the system.

3. Can connected particles have different masses?

Yes, connected particles can have different masses. In this case, the acceleration of the system will be dependent on the mass and net force of each individual particle.

4. How do you determine the tension in a string connecting two particles?

To determine the tension in a string connecting two particles, you must first draw a free body diagram of the system and identify all the forces acting on the particles. Then, use Newton's second law to set up equations for each particle and solve for the tension in the string.

5. Can connected particles move independently of each other?

No, connected particles cannot move independently of each other. They are linked by a physical connection, so their movements will be affected by each other. However, the individual particles may have different velocities or accelerations depending on their masses and the forces acting on them.

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