(i)1.5cm
(ii)4.5cm
(iii)10cm
<span>1) at rest his
weight is 840 N
=> 840N = mass * g => mass = 840 N / g = 840 N / 9.8 m/s^2 = 85.7 kg
2) as the elevator rises, his weight increases to 1050 N,
The reading of the scale is the norma force of it over the body of the person.
And the equation for the force is: Net force = mass * acceleration = normal force - weight at rest
=> mass * acceleration = 1050 N - 840 N = 210 N
acceleration = 210 N / mass = 210 N / 85.7 kg = 2.45 m/s^2 (upward)
3) when the elevator slows to a stop at the 10th
floor, his weight drops to 588 N
=> mass * acceleration = 588 N - 840 N = - 252 N
=> acceleration = - 252 N / 85.71 kg = - 2.94 m / s^2 (downward)
Answer:
Acceleration at the beginning of the trip 2.45 m/s^2 upward
Acceleration at the end of the trip 2.94 m/s^2 downward
</span>
<span>Since there is no friction, conservation of energy gives change in energy is zero
Change in energy = 0
Change in KE + Change in PE = 0
1/2 x m x (vf^2 - vi^2) + m x g x (hf-hi) = 0
1/2 x (vf^2 - vi^2) + g x (hf-hi) = 0
(vf^2 - vi^2) = 2 x g x (hi - hf)
Since it starts from rest vi = 0
Vf = squareroot of (2 x g x (hi - hf))
For h1, no hf
Vf = squareroot of (2 x g x (hi - hf))
Vf = squareroot of (2 x 9.81 x 30)
Vf = squareroot of 588.6
Vf = 24.26
For h2
Vf = squareroot of (2 x 9.81 x (30 – 12))
Vf = squareroot of (9.81 x 36)
Vf = squareroot of 353.16
Vf = 18.79
For h3
Vf = squareroot of (2 x 9.81 x (30 – 20))
Vf = squareroot of (20 x 9.81)
Vf = 18.79</span>
A scientific theory is different from a hypothesis because a theory is a educated guess that is being worked on and proven correct and a hypothesis is a educated guess it is a guess that needs to be proven.
