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3 years ago

A sprinter speeds up to 3 m/s during the last 2 seconds of the race with an

Physics

1 answer:

quester [9]3 years ago

4 0

Answer:

The initial speed of the sprinter was 2.2 m/s

Explanation:

Constant Acceleration Motion

It's a type of motion in which the velocity of an object changes by an equal amount in every equal period of time.

The following relation applies:

$v_f=v_o+at$

Where a is the constant acceleration, vo the initial speed, vf the final speed, and t the time.

The sprinter speeds up from an unknown initial speed to vf=3 m/s in t=2 seconds with an acceleration of $a=0.4~m/s^2$ .

To find the initial speed, we solve the equation for vo:

$v_o=v_f-at$

Substituting the values:

$v_o=3-0.4*2$

$v_o=3-0.8$

$v_o=2.2~m/s$

The initial speed of the sprinter was 2.2 m/s

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We have thatThe options that define Speed, Velocity,Acceleration.

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Choose the correct definitions of speed, velocity, and acceleration. Check all that apply.

Acceleration tells us in which direction the object is going. Speed is the rate of change of velocity in time.
Acceleration is the rate of change of velocity in time.
Velocity is used to describe changes in the movement direction of the object. Acceleration tells us how far the object will go in a certain amount of time.
Velocity is used to describe how fast the object is moving and tells us in which direction it is going.
Speed is used to describe how fast the object is moving.
Velocity is the rate of change of speed in time.

Speed is used to describe how fast the object is moving and tells us in which direction it is going.

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Acceleration is the rate of change of velocity in time.

Velocity is used to describe how fast the object is moving and tells us in which direction it is going.

Speed is used to describe how fast the object is moving without its direction in consideration

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The options that define Speed, Velocity,Acceleration.

Speed is used to describe how fast the object is moving.

Acceleration is the rate of change of velocity in time.

Velocity is used to describe how fast the object is moving and tells us in which direction it is going.

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2 years ago

A pitcher throws a softball toward home plate. When the ball hits the catcher’s mitt, its horizontal velocity is 32 meters/secon

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To calculate the force of impact F, first lets calculate the acceleration a of the ball:

a=v/t where v is the velocity of the ball and t is time

a=32/0.8=40 m/s²

To get the force F we need the Newtons second law:

F=m*a where m is the mass of the ball and a is the acceleration.

F=m*a= 0.2*40 = 8 N

So the impact force is F= 8 N.

5 0

3 years ago

Read 2 more answers

At 20 C, a steel rod of length 40.000 cm and a brass rod

balandron [24]

Answer:

a. stress in steel rod is -9.6 X 10⁷pa while stress in brass rod is -7.2 X 10⁷pa

b. new junction from steel rod is 40.0192cm while new junction from brass rod is 30.024cm

Explanation:

Step 1: identify the given parameters and standard parameters

⇒Steel rod: length of rod = 40.000 cm

Young modulus(Υ) = 20 X 10¹⁰ pa

coefficient of linear expansion(α) = 1.2 X 10⁻⁵ K⁻¹

stress in the rod =?

⇒Brass rod: length of rod = 30.000 cm

Young modulus(Υ) = 9 X 10¹⁰ pa

coefficient of linear expansion(α) = 2.0 X 10⁻⁵ K⁻¹

stress in the rod =?

--------------------------------------------------------------------------------------------

Step 2: calculate the stress in each rod

⇒Steel rod: stress in the rod = -Y*α*ΔT

= (-20 X 10¹⁰ pa) (1.2 X 10⁻⁵ K⁻¹)(60-20)K

= (-20 X 10¹⁰ pa) (1.2 X 10⁻⁵ K⁻¹)(40)K

= -9.6 X 10⁷ pa

--------------------------------------------------------------------------------------------

⇒Brass rod: stress in the rod = -Y*α*ΔT

= (-9 X 10¹⁰ pa) (2.0 X 10⁻⁵ K⁻¹)(60-20)K

= (-9 X 10¹⁰ pa) (2.0 X 10⁻⁵ K⁻¹)(40)K

= -7.2 X 10⁷ pa

--------------------------------------------------------------------------------------------

∴ stress in steel rod is -9.6 X 10⁷pa while stress in brass rod is -7.2 X 10⁷pa

--------------------------------------------------------------------------------------------

Step 3: calculate the new length of each rod

⇒Steel rod: New length = ΔL + L₀

ΔL = α*L₀*ΔT

ΔL = (1.2 X 10⁻⁵ K⁻¹)(40cm)(40)K

ΔL = 1920 X 10⁻⁵ cm = 0.0192cm

New length = ΔL + L₀ = 0.0192cm + 40cm

New length = 40.0192cm

--------------------------------------------------------------------------------------------

⇒Brass rod: New length = ΔL + L₀

ΔL = α*L₀*ΔT

ΔL = (2.0 X 10⁻⁵ K⁻¹)(30cm)(40)K

ΔL = 2400 X 10⁻⁵ cm = 0.024cm

New length = ΔL + L₀ = 0.024cm + 30cm

New length = 30.024cm

--------------------------------------------------------------------------------------------

Therefore, new junction from steel rod is 40.0192cm while new junction from brass rod is 30.024cm

8 0

3 years ago