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
Nezavi [6.7K]
3 years ago
5

A 7.5­kg block is sliding down a wall with constant velocity. The coefficient of static friction between the block and the wall

is μ s = 0.70. The coefficient of kinetic friction between the block and the wall is μ k = 0.40. What is the magnitude of the force (in N) pressing the block against the wall? Use g = 9.79 m/s2
Physics
1 answer:
weqwewe [10]3 years ago
8 0
Ok, a couple of things have to be accounted for here.  First, since the block is moving relative to the wall we have to use the kinetic coefficient of friction, 0.40.  The second consideration is that since the block is moving at a constant velocity, the acceleration is zero.  This means, by Newton's second Law, that the net force is zero.  So the force of gravity must be equal to the friction force of the wall resisting its fall. This friction force is the product of the normal force (which we are seeking) and the kinetic coefficient of friction. We can then set these two forces equal:

F_{gravity}=mg \\  \\ F_{friction}=F_{norm} \mu_k \\  \\ mg=F_{norm} \mu_k \\  \\ F_{norm}= \frac{mg}{ \mu_k} \\  \\  F_{norm}= \frac{7.5(9.79)}{0.4}=183.6N


You might be interested in
Which of the following units are fundamental units in the S.I. system of measurement
Nataliya [291]
Is recommend attaching the answer choices; Meters, Liters, Grams are three basic ones
8 0
3 years ago
Read 2 more answers
A 2.1 kg block is dropped from rest from a height of 5.5 m above the top of the spring. When the block is momentarily at rest, t
ella [17]

Answer:

The speed of the block is 8.2 m/s

Explanation:

Given;

mass of block, m = 2.1 kg

height above the top of the spring, h = 5.5 m

First, we determine the spring constant based on the principle of conservation of potential energy

¹/₂Kx² = mg(h +x)

¹/₂K(0.25)² = 2.1 x 9.8(5.5 +0.25)

0.03125K = 118.335

K = 118.335 / 0.03125

K = 3786.72 N/m

Total energy stored in the block at rest is only potential energy given as:

E = U = mgh

U = 2.1 x 9.8 x 5.5 = 113.19 J

Work done in compressing the spring to 15.0 cm:

W = ¹/₂Kx² = ¹/₂ (3786.72)(0.15)² = 42.6 J

This is equal to elastic potential energy stored in the spring,

Then, kinetic energy of the spring is given as:

K.E = E - W

K.E = 113.19 J - 42.6 J

K.E = 70.59 J

To determine the speed of the block due to this energy:

KE =  ¹/₂mv²

70.59 =  ¹/₂ x 2.1 x v²

70.59 = 1.05v²

v² = 70.59 / 1.05

v² = 67.229

v = √67.229

v = 8.2 m/s

8 0
3 years ago
Read 2 more answers
If you lift a five pound object 18 inches how many joules of energy did yo use?
kogti [31]
The work is 90 as 5 times 18

4 0
2 years ago
Determine whether the variable is qualitative or quantitative. Favorite sport. Is the Variable Qualitative or Quantitative?
Over [174]
The variable is qualitative, 
the quantitative variables are those that can be specified by a numeric value.
4 0
3 years ago
Two identical twins hold on to a rope, one at each end, on a smooth, frictionless ice surface. They skate in a circle about the
777dan777 [17]

Answer:

Part a)

L = 2683.2 kg m^2/s

Part b)

v' = 8.60 m/s

Part c)

W = 4326.7 J

Explanation:

Part a)

As we know that there is no external torque on the system of two twins

so here we will use

L = mv r + mvr

L = 2(78 \times 4.30 \times 4)

L = 2683.2 kg m^2/s

Part b)

Since angular momentum is conserved here as there is no external torque

so we will have

2(m v r) = 2( m v' \frac{r}{2})

v' = 2v

v' = 8.60 m/s

Part c)

Work done by both of them = change in kinetic energy

so we have

W = 2(\frac{1}{2}mv'^2 - \frac{1}{2}mv^2)

W = m(v'^2 - v^2)

W = 78(8.60^2 - 4.3^2)

W = 4326.7 J

5 0
3 years ago
Other questions:
  • An aluminium bar 600mm long1 with diameter 40mm, has a hole drilled in the centre of the bar. The hole is 30mm in diameter and i
    7·1 answer
  • A small ball is attached to one end of a rigid rod with negligible mass. The ball and the rod revolve in a horizontal circle wit
    5·1 answer
  • Predict which atom has the higher ionization energy. Na Al
    14·1 answer
  • When the Earth is positioned between the Moon and the Sun the following are possible:
    15·1 answer
  • A car travels a distance of 74 meters in 7 seconds. What is the average speed of the car?
    15·1 answer
  • What is the surface temperature of Sirius B and A, in kelvins?​
    9·1 answer
  • A rightward force of 4.0 N is exerted upon an object for a distance of 3.0 meters.
    14·1 answer
  • Of the following statement: Choose the Variable<br><br> X = 4 m
    15·1 answer
  • A 60 kg gorilla named Anthony Falcon is standing on his skateboard. This is on planet Erf,
    8·1 answer
  • A lens of focal length 10.0 cm
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!