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damaskus
2 months ago
9

When you skid to a stop on your bike, you can significantly heat the small patch of tire that rubs against the road surface. Sup

pose a person skids to a stop by hitting the brake on his back tire, which supports half the 90 kg combined mass of the bike and rider, leaving a skid mark that is 42 cm long. Assume a coefficient of kinetic friction of 0.80.
How much thermal energy is deposited in the tire and the road surface?

Express your answer with the appropriate units.
Physics
1 answer:
Sav [3.1K]2 months ago
3 0

Answer:

W_f = 148.17J

Explanation:

The friction created between the tire and the ground generates thermal energy as force is applied during skidding.

The mentioned force relates to half the impact on the rear tire, resulting in a calculated normal force of,

N=\frac{mg}{2} = \frac{90*9.8}{2} = 441N

The work executed is determined by the frictional force and the distance covered,

W_f = fd = \mu_k Nd

Where \mu_k [/ tex] is the coefficient of kinetic frictionN is the normal force previously found d is the distance traveled,Replacing,[tex]W_f = (0.80)(441)(0.42)

The thermal energy produced from the work done is,

W_f = 148.17J

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During a snowball fight two balls with masses of 0.4 and 0.6 kg, respectively, are thrown in such a manner that they meet head-o
Yuliya22 [3333]

Answer:

The snowball's speed after the impact is 3 m/s

Explanation:

Given the following:

mass of each ball

m₁ = 0.4 Kg

m₂ = 0.6 Kg

initial speed of both balls = v₁ = 15 m/s

Speed of 1 Kg mass post-collision =?

Applying conservation of momentum

m₁ v₁ - m₂ v₁ = (m₁+m₂) V

A negative velocity indicates that the second ball moves in the opposite direction.

0.4 x 15 - 0.6 x 15 = (1) V

Therefore,

V = - 3 m/s

Consequently,

The snowball's speed following the collision is 3 m/s

8 0
2 months ago
A copper sphere was moving at 25 m/s when it hit another object. This caused all of the KE to be converted into thermal energy f
kicyunya [3294]

Answer:

\Delta T = 0.81 ^oC

Explanation:

According to the principle of energy conservation

all kinetic energy will change into thermal energy to increase its temperature

\frac{1}{2}mv^2 = ms\Delta T

Next, divide both sides by the object's mass

\frac{1}{2}v^2 = s\Delta T

the resulting temperature change is expressed as

\Delta T = \frac{v^2}{2s}

\Delta T = \frac{25^2}{2\times 387}

\Delta T = 0.81^oC

3 0
2 months ago
For a given initial projectile speed Vo, calculate what launch angle A gives the longest range R. Show your work, don't just quo
ValentinkaMS [3465]
The ideal launch angle of 45° for achieving the greatest horizontal distance is only applicable when the starting height matches the final height. 

<span>In this scenario, you can demonstrate it as follows: </span>

<span>the initial velocity is Vo </span>
<span>the launch angle is α </span>

<span>the initial vertical velocity is </span>
<span>Vv = Vo×sin(α) </span>

<span>horizontal velocity becomes </span>
<span>Vh = Vo×cos(α) </span>

<span>the total flight duration is the period required to return to a height of 0 m, thus </span>
<span>d = v×t + a×t²/2 </span>
<span>where </span>
<span>d = distance = 0 m </span>
<span>v = initial vertical velocity = Vv = Vo×sin(α) </span>
<span>t = time =? </span>
<span>a = gravitational acceleration = g (= -9.8 m/s²) </span>
<span>therefore </span>
<span>0 = Vo×sin(α)×t + g×t²/2 </span>
<span>0 = (Vo×sin(α) + g×t/2)×t </span>
<span>t = 0 (obviously, the projectile is at height 0 m at time = 0s) </span>
<span>or </span>
<span>Vo×sin(α) + g×t/2 = 0 </span>
<span>t = -2×Vo×sin(α)/g </span>

<span>Now let's examine the horizontal distance. </span>
<span>r = v × t </span>
<span>where </span>
<span>r = horizontal range =? </span>
<span>v = horizontal velocity = Vh = Vo×cos(α) </span>
<span>t = time = -2×Vo×sin(α)/g </span>
<span>therefore </span>
<span>r = (Vo×cos(α)) × (-2×Vo×sin(α)/g) </span>
<span>r = -(Vo)²×sin(2α)/g </span>

<span>To find the extreme points of r (max or min) with respect to α, the first derivative of r with regards to α must be determined and set to 0. </span>

<span>dr/dα = d[-(Vo)²×sin(2α)/g] / dα </span>
<span>dr/dα = -(Vo)²/g × d[sin(2α)] / dα </span>
<span>dr/dα = -(Vo)²/g × cos(2α) × d(2α) / dα </span>
<span>dr/dα = -2 × (Vo)² × cos(2α) / g </span>

<span>As Vo and g are constants that are not equal to 0, the only solution for dr/dα to equal 0 is when </span>
<span>cos(2α) = 0 </span>
<span>2α = 90° </span>
<span>α = 45° </span>
4 0
1 month ago
An electric buzzer is activated, then sealed inside a glass chamber. When all of the air is pumped out of the chamber, how is th
ValentinkaMS [3465]
The intensity of the sound increases because sound waves are mechanical waves, meaning they cannot move through a vacuum and require a medium to propagate.
4 0
2 months ago
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