A load of mass 80kg is placed in a lift. Calculate the reaction between the floor of the lift and the load when the lift moves upwards:
(i) at constant velocity,
(ii) with an acceleration 2ms
2 [Take g 9.8ms 2].
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To calculate the reaction between the floor of the lift and the load, we need to consider the forces acting on the load in both scenarios.
(i) When the lift moves upwards at a constant velocity, the acceleration is zero. In this case, the upward force exerted by the floor of the lift (reaction force) is equal in magnitude and opposite in direction to the gravitational force acting on the load.
The gravitational force acting on the load can be calculated using the formula:
Force = mass x acceleration due to gravity
F_gravity = m x g
F_gravity = 80 kg x 9.8 m/s^2
F_gravity = 784 N
Since the velocity is constant, the upward force exerted by the floor (reaction force) must be equal to the gravity force acting on the load:
Reaction force = F_gravity = 784 N
Therefore, the reaction between the floor of the lift and the load is 784 N.
(ii) When the lift moves upwards with an acceleration of 2 m/s^2, we need to consider both the gravitational force and the additional force due to acceleration.
The gravitational force acting on the load remains the same:
F_gravity = m x g = 80 kg x 9.8 m/s^2 = 784 N
To calculate the additional force, we use the formula:
Force = mass x acceleration
F_additional = m x a
F_additional = 80 kg x 2 m/s^2
F_additional = 160 N
The total force acting on the load is the sum of the gravitational force and the additional force:
Total force = F_gravity + F_additional
Total force = 784 N + 160 N
Total force = 944 N
Therefore, the reaction between the floor of the lift and the load when the lift moves upwards with an acceleration of 2 m/s^2 is 944 N.
No problem, feel free to ask any question you have!
Ssdg2
(i) if the velocity is constant there is no acceleration so the force up from the floor = weight down = m g = 80*9.8 Newtons
(i) If we accelerate UPWARDS at 2 m/s^2
then Fup-Fdown = m a
Fup - m g = m a
Fup = 80(9.8 + 2) Newtons