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Aleks04 [339]
2 years ago
9

A 100-meter sprint is a race using only the straight side of a racetrack. A 400-meter sprint is a race that makes one complete l

ap around a racetrack. Why are velocity and speed the same for 100-meters sprint but not a 400-m sprint?
Physics
2 answers:
Effectus [21]2 years ago
5 0
Velocity is a vector quantity and depends on both speed and direction.
In 100m you only travel straight in one direction.
But in 400m you have to turn corners and then go back the way you came, and then turn another corner, you're changing direction - hence changing velocity, even if the speed is the same.
DanielleElmas [232]2 years ago
3 0

In the 100-m sprint, the displacement is 100 meters and the distance is 100 meters. This means speed and velocity are the same for the 100-m sprint. In the 400-m sprint, the distance is 400-m, but the runners stop at the same place they start so the displacement is zero. Zero displacement means zero velocity.

yw!

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Some plants disperse their seeds when the fruit splits and contracts, propelling the seeds through the air. The trajectory of th
Anton [14]

Answer:

Option B, 93 cm

Explanation:

An diagram of the seed's motion is attached to this solution.

This is very close to a projectile motion question. And the quantity to be calculated, how far along the grant a seed released would travel is called the Range.

And this would be obtained from the equations of motion,

First of, the height of the plant is related to some quantities of the motion with this relation.

H = u(y) t + 0.5g(t^2)

U(y) = initial vertical component of velocity = 0 m/s, H = height at which motion began, = 20cm = 0.2 m

That means t = √(2H/g)

The horizontal distance covered, R,

R = u(x) t + 0.5g(t^2) = u(x) t (the second part of the equation goes to zero as the vertical component of the acceleration of this motion is 0)

(substituting the t = √(2H/g) derived from above

R = u(x) √(2H/g)

Where u(x) = the initial horizontal component of the bomb's velocity = maximum initial speed, that is, 4.6 m/s, H = vertical height at which the seed was released = 20 cm = 0.2 m, g = acceleration due to gravity = 9.8 m/s2

R = 4.6 √(2×0.2/9.8) = 0.929 m = 0.93 m = 93 cm. Option B.

QED!

6 0
2 years ago
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Julius competes in the hammer throw event. the hammer has a mass of 7.26 kg and is 1.215 m long. what is the centripetal force o
TEA [102]
Centripetal force <span>a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving. It is calculated by the expression:

F = mv^2/r

where m is the mass, v is the velocity and r is the radius.

F = 7.26(31.95)^2 / (1.215) = 6100 N</span>
8 0
2 years ago
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A student lifts a set of books off a table and places them in the upper shelf of a book case which is 2 meters above the table.
AfilCa [17]
The work done is the product between the intensity of the force applied F, the amount of the displacement d of the book and the cosine of the angle \theta between the direction of the force and the direction of the displacement:
W=Fd \cos \theta
In our problem, the student is lifting the book, so he is applying a force directed upward, and the book is moving upward, so F and d are parallel and therefore the angle is zero, so \cos \theta = \cos 0=1
Therefore, the work done is
W=Fd=(5 N)(2 m)=10 J
6 0
2 years ago
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A baseball of mass m = 0.49 kg is dropped from a height h1 = 2.25 m. It bounces from the concrete below and returns to a final h
Brilliant_brown [7]

Answer:

Explanation:

Impulse = change in momentum

mv - mu , v and u are final and initial velocity during impact at surface

For downward motion of baseball

v² = u² + 2gh₁

= 2 x 9.8 x 2.25

v = 6.64 m / s

It becomes initial velocity during impact .

For body going upwards

v² = u² - 2gh₂

u² = 2 x 9.8 x 1.38

u = 5.2 m / s

This becomes final velocity after impact

change in momentum

m ( final velocity - initial velocity )

.49 ( 5.2 - 6.64 )

= .7056 N.s.

Impulse by floor in upward direction

= .7056 N.s

6 0
2 years ago
If a 20.0 g object at a temperature of 35.0∘C has a specific heat of 2.89Jg∘C, and it releases 450. J into the atmosphere, what
nataly862011 [7]

Answer:

The final temperature of the object will be 42.785 °C

Explanation:

When the heat added or removed from a substance causes a change in temperature in it, this heat is called sensible heat.

In other words, sensible heat is the amount of heat that a body absorbs or releases without any changes in its physical state (phase change), so that the temperature varies.

The equation for calculating the heat exchanges in this case is:

Q = c * m * ΔT

where Q is the heat exchanged by a body of mass m, constituted by a substance of specific heat c and where ΔT is the variation in temperature.

In this case:

  • Q= 450 J
  • c= 2.89 \frac{J}{g*C}
  • m= 20 g
  • ΔT= Tfinal - Tinitial= Tfinal - 35 °C

Replacing:

450 J= 2.89 \frac{J}{g*C} *20 g* (Tfinal - 35°C)

Solving for Tfinal:

\frac{450 J}{2.89\frac{J}{g*C}*20g} =Tfinal -35C

7.785 °C=Tfinal - 35°C

7.785 °C + 35°C= Tfinal

42.785 °C=Tfinal

<u><em>The final temperature of the object will be 42.785 °C</em></u>

8 0
2 years ago
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