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
OlgaM077 [116]
3 years ago
6

A dockworker loading crates on a ship finds that a 21-kg crate, initially at rest on a horizontal surface, requires a 73-N horiz

ontal force to set it in motion. However, after the crate is in motion, a horizontal force of 55 N is required to keep it moving with a constant speed. Find the coefficients of static and kinetic friction between crate and floor. static friction kinetic friction
Physics
1 answer:
Nataliya [291]3 years ago
5 0

1) Static friction coefficient: 0.355

The crate is initially at rest. The crate remains at rest until the horizontal pushing force is less than the maximum static frictional force.

The maximum static frictional force is given by

F_s = \mu_s mg

where

\mu_s is the static coefficient of friction

m = 21 kg is the mass of the crate

g = 9.8 m/s^2 is the acceleration due to gravity

The horizontal force required to set the crate in motion is 73 N: this means that this is the value of the maximum static frictional force. So we have

F_s=73 N

Using this information into the previous equation, we can find the coefficient of static friction:

\mu_s = \frac{F}{mg}=\frac{73 N}{(21 kg)(9.8 m/s^2)}=0.355

2) Kinetic friction coefficient: 0.267

Now the crate is in motion: this means that the kinetic friction is acting on the crate, and its magnitude is

F_k = \mu_k mg (1)

where

\mu_k is the coefficient of kinetic friction

There is a horizontal force of

F = 55 N

pushing the crate. Moreover, the speed of the crate is constant: this means that the acceleration is zero, a = 0.

So we can write Newton's second law as

F-F_k = ma = 0

And by substituting (1), we can find the value of the coefficient of kinetic friction:

F-\mu_k mg = 0\\\mu_k = \frac{F}{mg}=\frac{55 N}{(21 kg)(9.8 m/s^2)}=0.267

You might be interested in
What is a Pulley why is it used​
aleksley [76]

Answer:

A simple pulley is a wheel with a rope that allows you to pull one end and have it lift whatever is on the other end. A modern, common example of this is a crane, often used in construction.

Explanation:

4 0
2 years ago
A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 43 kg barbell straight up fro
Tasya [4]

Answer:

A. 231.77 J

B. 5330.71 J

C. 46 donuts

Explanation:

A. To lift the barbell once, she will have to extend it the full length of her arm. The work done will then be:

W = F * d

Where the force is the weight of the barbell.

F = m * g

Hence, the work done in lifting the barbell is:

W = m * g * d

W = 43 * 9.8 * 0.55

W = 231.77 J

B. If she does 23 repetitions, the total energy she expend will be equal to the Potential energy when the barbell is lifted multiplied by 23:

E = 23 * m * g * d

E = 23 * 231.77

E = 5330.71 J

C. 1 Joule = 4.184 calories

5330.71 Joules = 5330.71 * 4.184 = 22303.69

If 1 donut contains 490 calories, the number of donuts she will need will be:

N = 22303.69/490 = 45.5 donuts or 46 donuts

5 0
3 years ago
Someone please help! It is a few science questions. Fairly easy!
borishaifa [10]
1) 0.92 * 100 = 92 <Solve using the formula which is:
Mass=Density×Volume
M=D*V

2) 3.98 ml

3) V=L*W*H (Length  × Width × Height)

5*2*4=40
\frac{300}{40} =7.5 (Answer=7.5)
3 0
3 years ago
Read 2 more answers
2 76 Consider a household that uses 14,000 kWh of elec- (tricity per year and 3400 L of fuel oil during a heating sea- son. The
NNADVOKAT [17]

Answer:

The total amount of CO₂ produced will be  = 20680 kg/year

The reduction in the amount of CO₂ emissions by that household per year = 3102 kg/year

Explanation:

Given:

Power used by household = 14000 kWh

Fuel oil used = 3400 L

CO₂ produced of fuel oil = 3.2 kg/L

CO₂ produced of electricity = 0.70 kg/kWh

Now, the total amount of CO₂ produced will be = (14000 kWh × 0.70 kg/kWh) + (3400 L × 3.2 kg/L)

⇒ The total amount of CO₂ produced will be = 9800 + 10880 = 20680 kg/year

Now,

if the usage of electricity and fuel oil is reduced by 15%, the reduction in the amount of the CO₂ emission will be = 0.15 × 20680 kg/year = 3102 kg/year

6 0
3 years ago
Transverse waves travel with a speed of 20.0 m/s on a string under a tension of 6.00 N. What tension is required for a wave spee
marta [7]

Based on the sped of the waves and the tension as well as the needed wave speed, the required tension is 13.5 N.

<h3>What is the required tension?</h3>

Given the initial tension and speed, the tension that is required can be found by the formula:

= Initial tension x (Required speed / Initial speed)²

Solving gives:

= 6 x (30 / 20)²

= 6 x 9/4

= 13.5 N

In conclusion, the tension required is 13.5N.

Find out more on the tension on a wire at brainly.com/question/14290894.

#SPJ4

3 0
1 year ago
Other questions:
  • The net force acting on a 50kg crate is 0 N. what is the crates accelratiin
    11·1 answer
  • The maximum torque on a set of 20 square loops with edge lengths of 6 cm in a 4.0 T magnetic field is:A) 0.288 N-m.B) 4.8 N-m.C)
    14·1 answer
  • According to Newton's third law of motion, if this snowy owl wants to increase its altitude, what must it do?
    5·2 answers
  • A uniform electric field is pointing in x direction. The magnitude of the electric field is 10 N/C. The filed makes an angle of
    8·1 answer
  • The Kentucky Derby, the first leg of horse racing’s Triple Crown, was won by a time of 122.2 s. If the race covers 2011.25 m, wh
    15·2 answers
  • Which example best demonstrates how unbalanced forces change the speed of an object's motion?
    5·1 answer
  • Compare the number of electrons with the number of protons in a charged object.
    8·1 answer
  • A substance burns in the presence of oxygen.
    10·2 answers
  • The block in the figure below has a mass of 5.1 kg and it rests on an incline of angle . You pull on the rope with a force F = 3
    10·1 answer
  • Amber is a<br>(a) metal<br>(b) rubber<br>(c) resin<br>(d) sugar<br>​
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!