If you stand in a lift that is accelerating downwards at a rate of 2 m s-2, you will experience an apparent upthrust that acts against your weight. Your weight (the force that acts in a downward direction due to gravity) is:
W = m g
= mass x gravitational field strength
On Earth, g is about 9.8 N kg-1 or 9.8 m s-2 (both units are equivalent)
W = 50 kg x 9.8 N kg-1
= 490 N (in a downward direction)
The upward force due to your acceleration is given by Newton's second law:
F = m a
= mass x acceleration
= 50 kg x 2 m s-2
= 100 N (in an upward direction)
So the overall weight you feel is the difference between them. So:
W = 490 - 100
= 390 N
We have no way to calculate that, unless you also tell us either his mass, or else his weight on motionless ground, like when the scale is on the bathroom floor.
You weigh less only while the elevator's upward speed is decreasing, or downward speed is increasing. In each case, the acceleration of the elevator is in a direction opposite to the acceleration of gravity. The result of that is that the total acceleration acting on you is less than usual, and your weight is less. Note that in a sealed container, such as a space ship or an elevator, there's no way for you to tell the difference between acceleration and a gravitational field.
If the elevator accelerates, the acceleration will provide an additional apparent force.
If the elevator's speed is constant (acceleration is zero), regardless of whether it's up or down,then your weight in it is the same as your normal weight on the ground.It should be easy to carry a bathroom scale onto an elevator with you some day and check it out.
When the elevator is still the force of gravity due to your weight pressing downwards on the floor is equalled exactly by the floor pushing you upwards with the same force. When the elevator rises you feel a little heavier, and the elevator is pushing upwards with the same increased force. When the elevator descends you feel that you lose a little weight, and the floor pushes up at you with the equally reduced force, so you descend.
That's the force that engineers call the "weight" of the elevator car. As long as the elevator stays on Earth, its weight is constant, whether it's rising, falling, stopped, or out of order. On or near the Earth's surface, the weight of 1,140 kilograms of mass is about 11,180 Newtons (2,513.3 pounds).
only if it equaled acceleration due to gravity (about 9.8 (m/s)/s)
That's the force that engineers call the "weight" of the elevator car. As long as the elevator stays on Earth, its weight is constant, whether it's rising, falling, stopped, or out of order. On or near the Earth's surface, the weight of 1,140 kilograms of mass is about 11,180 Newtons (2,513.3 pounds).
We must use: (Force) = (Mass) x (Acceleration) Force = 400 N Acceleration = 9.8 m/(s^2) Mass = M 400 N = ( M ) x ( 9.8 m/(s^2)) After calculating, we find the mass of the man to be 40.82 kg.
In physics, the force of gravity exerted on a body is called weight. Weight is often expressed in the formula W=mg, where W stands for weight, m stands for mass and g stands for gravitational acceleration.
Draw an arrow pointing upwards for the tension force and an arrow pointing downwards for the weight of the elevator which will be its mass times gravity (mg). Also, draw another arrow pointing downwards for any mass that may be inside the elevator (another mass times gravity arrow but for a separate weight) and add that value to that of the weight of the elevator. Depending on the direction that the elevator is moving (up or down) draw another arrow respectively and label it "a" for acceleration.
Your weight (the force you feel at the soles of your feet) in an elevator traveling at any constant speed in anydirection would be the same at any instant as it would be if you were in that elevator in the same place, stopped. For practical purposes, it would be the same as it would be when you're standing on the ground. Technically, weight changes with altitude, but for any existing building the difference between your weight at the lowest and highest points of the building will be so slight as to be undetectable. You'd probably lose more weight due to evaporation of moisture in perspiration and exhaled breath during the elevator ride than you would due to the slight reduction in gravity resulting from your moving a bit further from the surface of the Earth.In order for your perceived weight to change, there has to be an acceleration. Constant speed/velocity is not acceleration. You would feel a change in weight as the elevator slowed down or sped up, but you would feel your "normal" weight once the elevator reaches constant speed/velocity.