A 75 kg man is standing on a scale in an elevator. What does the scale read in newtons when he is:?

Question

a. not moving
b. moving upwards at constant velocity of 2 m/s
c. accelerating upwards at 2 m/s/s

Please explain these, my teacher said something about normal force and weight force but I'm confused what the scale reads now and I can't get any of these right on my webassign.

Answer 1

The normal force is the upward force that the floor of the elevator exerts on the bottom of the scale. The net force on the scale is equal to the difference of the man’s weight and the normal force. If the elevator is at rest or moving at a constant velocity, the acceleration is 0 m/s. This means the net force is 0 N. This means the magnitude of the normal force is equal to the magnitude of the man’s weight. In this the scale reading is equal to the man’s weight. When the elevator is accelerating upward, the normal force is greater than the man’s weight. In this case, the scale is actually supporting the man’s weight and causing the man to accelerate upward at 2 m/s^2.



Weight = 75 * 9.8 = 735 N



To determine the scale reading for accelerating upward, use the following equation.



F = Weight + m * a = 735 + 75 * 2 = 885 N



If you go to the website below, you will see drawings and equations for this type of problem.





http://hyperphysics.phy-astr.gsu.edu/hbase/elev.html



If you use 75 for the mass and 2 for the acceleration, you will see that the force is 885 N. The hyperphysics website is very helpful. I hope this helps you to understand how to solve this type of problem. If you need help in the future, you can contact me at the following email address.



[e-mail]

Answer 2

A 75 kg man is standing on a scale in an elevator. What does the scale show in newtons when he is :?

a. not moving

F1 = m*g = 75*9.8 = 735.00 N



b. moving upwards at constant velocity of 2 m/s

F2 = m*g = 75*9.8 = 735.00 N



c. accelerating upwards at 2 m/s^2

F3 = m*(g+a) = 75*(9.8+2.0) = 885.00 N

Answer 3

When you are at rest or moving at a constant velocity the weight (a.k.a gravitational force) and normal force are equal to each other because the net force must equal zero.

Fg= mass x gravity Fg= mass x acceleration



a) Fg = 75kg x 9.8 m/s/s

=735 N



b) Fg= 75kg x 9.8 m/s/s

= 735 N



c) You use the second equation here because you are no longer at rest/ constant velocity.

Fg= mass x acceleration

= 75 kg x 2 m/s/s

= 150 N