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
sdas [7]
3 years ago
9

A cross-country skier can complete a 7.5 km race in 45 min. What is the skier’s average speed?

Physics
2 answers:
Triss [41]3 years ago
8 0

<u>Answer</u>

2.7778 m/s


<u>Explanation</u>

Speed is rate of change of distance with time.

It is the distance covered in a unit time.  SI units of speed in m/s. Other units are Km/h, knots e.t.c

Average speed  = (total distance covered) / (total time taken)

                             = 7.5 Km / 45 Min

                             =  1/6 Km/Min

Or,

7.5Km = (7.5 × 1000) m = 7500 m

45 min = 45 × 60 2700 seconds

Average speed = 7500/2700

                           = 2.7778 m/s

Alecsey [184]3 years ago
7 0
To calculate for the average speed, we simply divide the total distance covered by the time it takes to travel that distance. In this case, we simply divide 7.5 km with 45 min. Therefore, the skier's average speed is 0.1667 km/min. Hope this helps.
You might be interested in
An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle
Dovator [93]

Answer:The velocity of the train is 3.84m/s

Explanation:

According to the Doppler effect, if the source is moving towards you then the apparent frequency of the sound emitted by the source is higher and if the source is moving away from you then the apparent frequency of the sound emitted by the source is smaller.

This is given by:

fo = V +-Vo/ V +-Vo × source

Where fo= observed frequency

V= velocity of sound

Vo= vo it of the observer

fsource= frequency the source

Given:

Observed frequency of the approaching train fo1= 452Hz

The observed frequency of train= fo2= 442Hz

Velocity of sound= 334m/s

Velocity of source=?

Train approaching the observer is given by:

fo1= V/(V - Vs)× source ...eq1

Train passes the student is given by:

fo2= V/(V - Vs)×source ...eq2

Divide eq1 by eq2

452/442 = (343+Vs)/(343 - Vs)

1.02 =(343+Vs)/(343 -Vs)

Cross multiply

1.02(343- Vs) = 343 + Vs

350.76 - 1.02Vs = 343 + Vs

Collecting like terms

350.76 -343= 1.02Vs+ Vs

7.76 = 2.02Vs

Vs= 7.76/2.02

Vs= 3.84m/s

4 0
3 years ago
Consider the potential energy diagram shown below. This graph shows the chemical potential energy in a reaction system over time
kolbaska11 [484]

Answer:

A. Endothermic reaction.

B. +150KJ.

C. 250KJ.

Explanation:

A. The graph represents endothermic reaction because the heat of the product is higher than the heat of the reactant.

B. Determination of the enthalpy change, ΔH for the reaction. This can be obtained as follow:

Heat of reactant (Hr) = 50KJ

Heat of product (Hp) = 200KJ

Enthalphy change (ΔH) =..?

Enthalphy change = Heat of product – Heat of reactant.

ΔH = Hp – Hr

ΔH = 200 – 50

ΔH = +150KJ

Therefore, the enthalphy change for the reaction is +150KJ

C. The activation energy for the reaction is the energy at the peak of the diagram.

From the diagram, the activation energy is 250KJ.

6 0
3 years ago
A ring with an 18mm diameter falls off a scientist's finger into the solenoid in the lab. The solenoid is 25 cm long, 5.0 cm in
Troyanec [42]

Answer:

The value is  \epsilon =  3.84 *10^{-5} \  V

Explanation:

From the question we are told that

  The diameter of the ring is  d =  18 \ mm  =  0.018 \  m

   The length of the solenoid is l = 25 \ cm  =  0.25 \ m

   The diameter of the solenoid is  D = 5.0 \ cm  = 0.05 \ m

    The number of turns is  N = 1500

   The change in  current in the solenoid is   \Delta  I   = 20 \ A

   The time taken is  \Delta  t  = 1 \ s

Generally the radius of the ring is  

     r = \frac{d}{2}

=>  r = \frac{0.018 }{2}

=>  r = 0.009 \ m

Generally the area of the ring is mathematically represented as  

      A = \pi r^2

=>   A = 3.142 *  0.009^2    

=>   A = 2.545 *10^{-4}\ m^2

Generally the induced emf is mathematically represented as

       \epsilon  =  A * \frac{dB}{dt}

Here    

         \frac{dB }{dt} =  \mu_o * \frac{N}{l} *\frac{ \Delta I }{\Delta t}

Here  \mu_o is the permeability of free space with value  

         \mu_o =  4\pi *10^{-7} \ N/A^2

So  

     \frac{dB }{dt} =   4\pi * 10^{-7} * \frac{1500}{0.25} *\frac{20 }{1}

=>  \frac{dB }{dt} =   0.150816\  T/s

So

     \epsilon =   0.150816 *  2.545 *10^{-4}

=>   \epsilon =  3.84 *10^{-5} \  V

3 0
3 years ago
What's a refractive medium that focuses light to a single point?
ss7ja [257]

Answer:

The convex lens is shaped so that all light rays that enter it parallel to its axis cross one another at a single point on the opposite side of the lens.

Explanation:

3 0
3 years ago
A 2 kg mass is free falling in the negative Y direction when a 10 N force is exerted in the minus X direction. What is the accel
lara31 [8.8K]

Answer:

The mass's acceleration is 5 m/s^2 in the minus X direction and 9,8 m/s^2 in the minus Y direction.

Explanation:

By applying the second Newton's law in the X and Y direction we found that in the minus X direction an external force of 10 N is exerted, while in the minus Y direction the gravity acceleration is acting:

X-direction balance force: -10 [N] = m.ax

Y-direction balance force: -m*9,8 \frac{m}{s^2} = m.ay

Where ax and ay are the components of the respective acceleration and m is the mass. By solving for each acceleration:

ax=(-10 [N]) / m

ay=-m*9,8\frac{m}{s^2} / m

Note that for the second equation above the mass is cancelled and, the Y direction acceleration is minus the gravity acceleration:

ay=-9,8\frac{m}{s^2}

For the x component aceleration we must replace the Newton unit:

N =\frac{kg.m}{s^2}

ax= -10 \frac{kg.m}{s^2} / (2 kg)

ax= - 5 \frac{m}{s^2}

6 0
3 years ago
Other questions:
  • Which of the following best illustrates chemical potential energy a dog Plane, gasoline gasoline, water moving down hill, a skyd
    8·1 answer
  • A cyclist is riding his bike up a mountain trail. When he starts up the trail, he is going 8 m/s. As the trail gets steeper, he
    15·1 answer
  • URGENT HELP! 
    8·2 answers
  • Sally is on a canoe that comes to a stop a small distance from the dock. Since it is such a small distance, Sally decides to jum
    13·1 answer
  • 1.) How much potential energy does an object with a mass of 3 kg have on top of a stand 12 meters
    13·1 answer
  • Find the force, in Newtons, on a rectangular metal plate with dimensions of 4 m by 8 m that is submerged horizontally in 9 m of
    6·1 answer
  • What is convection?<br> what is radiation ?<br> what conduction?
    5·1 answer
  • A person weighs 60 kg. The area under the foot of the person is 150 cm2. Find the pressure exerted on the ground by the person.
    8·1 answer
  • Question 1
    13·1 answer
  • A machine produces 4,000 J of work in 5 seconds. how much power does the machine produce.
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!