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I am Lyosha [343]
3 years ago
14

A professor drives off with his car (mass 870 kg), but forgot to take his coffee mug (mass 0.47 kg) off the roof. The coefficien

t of static friction between the mug and the roof is 0.7, and the coefficient of kinetic friction is 0.5. What is the maximum acceleration of the car, so the mug does not slide off?
Physics
1 answer:
SSSSS [86.1K]3 years ago
8 0

Answer:6.86 m/s^2

Explanation:

Given

mas of car=870 kg

coffee mug mass=0.47 kg

coefficient of static friction between mug and roof \mu _s= 0.7

Coefficient of kinetic Friction \mu _k=0.5

maximum car acceleration is \mu \times g

here coefficient of static friction comes in to action because mug is placed over car . If mug is moving relative to car then \mu _k is come into effect

a_{max}=0.7\times 9.8=6.86 m/s^2

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A stone is tossed horizontally from the highest point of a 95 m building and lands 105 m from the base of the building. Ignore a
aalyn [17]

Answer:

A) t = 4.40 s , B)   v = 23.86 m / s ,  c)  v_y = - 43.12 m / s , D)  v = 49.28 m/s

Explanation:

This is a projectile throwing exercise,

A) To know the time of the stone in the air, let's find the time it takes to reach the floor

          y = y₀ + v_{oy} t - ½ g t²

as the stone is thrown horizontally  v_{oy} = 0

          y = y₀ - ½ g t²

          0 = y₀ - ½ g t²

          t = √ (2 y₀ / g)

          t = √ (2 95 / 9.8)

          t = 4.40 s

B) what is the horizontal velocity of the body

          v = x / t

          v = 105 / 4.40

          v = 23.86 m / s

C) The vertical speed when it touches the ground

          v_y = v_{oy} - g t

          v_y = 0 - 9.8 4.40

          v_y = - 43.12 m / s

the negative sign indicates that the speed is down

D) total velocity just hitting the ground

          v = vₓ i ^ + v_y j ^

          v = 23.86 i ^ - 43.12 j ^

Let's use Pythagoras' theorem to find the modulus

          v = √ (vₓ² + v_y²)

          v = √ (23.86² + 43.12²)

           v = 49.28 m / s

we use trigonometry for the angle

          tan θ = v_y / vₓ

          θ = tan⁻¹ (-43.12 / 23.86)

            θ = -61

7 0
3 years ago
A 24 kg child slides down a 3.3-m-high playground slide. She starts from rest, and her speed at the bottom is 3.0 m/s.a. What en
Gelneren [198K]

Answer:

(a) Potential energy of the child is converted into the kinetic energy at the bottom off the slide and a part of which is lost into friction generating heat between the contact surfaces.

(b) U=668.16\ J

Explanation:

Given:

  • mass of the child, m=24\ kg
  • height of the slide, h=3.3\ m
  • initial velocity of the child at the slide, v_i=0 m.s^{-1}
  • final velocity of the child at the bottom of slide, v_f=3\ m.s^{-1}

(a)

∴The initial potential energy of the child is converted into the kinetic energy at the bottom off the slide and a part of which is lost into friction generating heat between the contact surfaces.

Initial potential energy:

PE=m.g.h

PE=24\times 9.8\times 3.3

PE=776.16\ J

Kinetic energy at the bottom of the slide:

KE=\frac{1}{2} m.v^2

KE= 0.5\times 24\times 3^2

KE= 108\ J

(b)

Now, the difference in the potential and kinetic energy is the total change in the thermal energy of the slide and the seat of her pants.

This can be given as:

U=PE-KE

U=776.16-108

U=668.16\ J

4 0
2 years ago
What<br> are the properties of magnets?
babymother [125]

Answer:

Attractive Property – Magnet

Explanation:

attracts ferromagnetic materials like iron, cobalt, and nickel. Repulsive Properties – Like magnetic poles repel each other and unlike magnetic poles attract each other. Directive Property – A freely suspended magnet always points in a north-south direction.

8 0
3 years ago
A 7.80 g bullet moving at 530 m/s penetrates a tree trunk to a depth of 5.40 cm. (a) Use work and energy considerations to find
True [87]

Answer:

a) F=20287.22N

b) t=2*10^-4s

Explanation:

E=1/2*m*v^2=0.5*7.8*10^-3kg*(530m/s)^2=1095.51J

The frictional force's work must be equal than the energy to stop the bullet.

So: W=F*d=F*0.054m=1095.51J, F=20287.22N

Considering the frictional force is constant, the bullet moves with constant aceleration.

a=F/m=20287.22N/7.8*10-2kg=2.6*10^6m/s^2

then d(t)=Vt-1/2*a*t^2,

5.4*10^-2m=530m/s*t-1.3*10^6m/s^2*t^2

I will calculate the time using the cuadratic formula:

\frac{-b+-\sqrt{b^{2}-4ac } }{2a}

with a=1.3*10^6, b=-530, c=5.4*10^-2

t=2*10^-4s

8 0
2 years ago
What is solar energy?
RoseWind [281]

Solar energy is energy that is produced using the sun's rays.

7 0
3 years ago
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