1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Bogdan [553]
3 years ago
7

Henry, whose mass is 95 kg, stands on a bathroom scale in an elevator. The scale reads 830 N for the first 3.8 s after the eleva

tor starts moving, then 930 N for the next 3.8 s. What is the elevator's speed 7.6 s after starting?
Physics
1 answer:
Delicious77 [7]3 years ago
3 0

Answer:

v= 4.0 m/s

Explanation:

  • When standing on the bathroom scale within the moving elevator, there are two forces acting on Henry's mass: Normal force and gravity.
  • Gravity is always downward, and normal force is perpendicular to the surface on which the mass is located (the bathroom scale), in upward direction.
  • Normal force, can adopt any value needed to match the acceleration of the mass, according to Newton's 2nd Law.
  • Gravity (which we call weight near the Earth's surface) can be  calculated as follows:

       F_{g} = m*g = 95 kg * 9.8 m/s2 = 930 N (1)

  • According to Newton's 2nd Law, it must be met the following condition:

       F_{net} = F_{g} -F_{n} = m*a\\  F_{net} = 930 N - 830 N = 100 N = 95 Kg * a

  • As the gravity is larger than normal force, this means that the acceleration is downward, so, we choose this direction as the positive.
  • Solving for a, we get:

       a =\frac{F_{net} }{m} =\frac{100 N}{95 kg} =  1.05 m/s2

  • We can find the speed after the first 3.8 s (assuming a is constant), applying the definition of acceleration as the rate of change of velocity:

        v_{f} = a* t = 1.05 m/s * 3.8 m/s = 4.0 m/s

  • Now, if during the next 3.8 s, normal force is 930 N (same as the weight), this means that both forces are equal each other, so net force is 0.
  • According to Newton's 2nd Law, if net force is 0, the object  is either or at rest, or moving at a constant speed.
  • As the elevator  was moving, the only choice is that it is moving at  a constant speed, the same that it had when the scale was read for the first time, i.e., 4 m/s downward.
You might be interested in
Why do you think football players are usually large in size?
kiruha [24]
Football players in the NFL are large in size due to their eating habits since as players they have to work out constantly to stay and shape and eat to gain weight and be strong, so its important for them to be strong against their opponents in gameplay. Football players sometimes take steroids which make their muscles stronger and harder, and also gives them a growth spurt but the effects are worse and makes them sicker, high blood pressure, and even more. 
8 0
3 years ago
Read 2 more answers
A grindstone of mass 12 kg and radius 0.3 m is initially rotating freely at 48 rad/sec. An axe is brought into contact with the
lesya [120]

Answer:

I = 0.54\,kg\cdot m^{2}

Explanation:

1) The moment of inertia of the grindstone is:

I = \frac{1}{2}\cdot m \cdot r^{2}

I = \frac{1}{2}\cdot (12\,kg)\cdot (0.3\,m)^{2}

I = 0.54\,kg\cdot m^{2}

4 0
3 years ago
Read 2 more answers
The equation of damped oscillations is given in the form x=0.05e^-0.25sin½πt (m). Find the velocity of an oscillating point at t
zhannawk [14.2K]

Explanation:

The logarithmic damping decrement of a mathematical pendulum is DeltaT=0.5. How will the amplitude of oscillations decrease during one full oscillation of the pendulum

8 0
3 years ago
Read 2 more answers
26. ____________ is a chemical reaction between an acid and a base that produces a salt and water
Anuta_ua [19.1K]
26 neutralization reaction;
27 positive ions;
28 titrations;
29 bases;
30 buffers
3 0
3 years ago
Only known planet able to support life
Nataly [62]
1 is the correct answer
3 0
3 years ago
Other questions:
  • What happens to the frequency of a wave if its energy increases?
    14·2 answers
  • 8. The legs of a young man are each 0.650 meters long. What is his maximum walking speed?
    5·1 answer
  • A 60.0-kg person is in an elevator with a mass of 2000 kg. The elevator moves vertically up through a distance of 24.0 m with a
    9·1 answer
  • Creek and Cold stand back-to-back and walk in opposite directions for $40$ yards each. Each of them then turns left and walks an
    9·1 answer
  • To reduce inductive reactance, what devices are normally placed on transmission or distribution lines?
    6·1 answer
  • A baseball pitcher loosens up his pitching arm. He tosses a 0.20-kg ball using only the rotation of his forearm, 0.28 m in lengt
    5·1 answer
  • What does the area between the line and the x axis represent on a velocity vs time graph
    14·1 answer
  • Newton's First Law is:
    6·1 answer
  • An amoeba has 1.00 x 1016 protons and a net charge of 0.300 pC. Assuming there are 1.88 x 106 fewer electrons than protons, If y
    14·1 answer
  • A 25kg child resting at the top of a 2 meter slide has how much potential energy?
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!