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
Grace [21]
3 years ago
14

A car moves uphill at 40 km/h and then back downhill at 60 km/h. What is the average speed for the round trip?

Physics
1 answer:
jok3333 [9.3K]3 years ago
5 0

Answer:

S_a_v_e_r_a_g_e=48km/h

Explanation:

Ok, the average speed can be calculate with the next equation:

S_a_v_e_r_a_g_e=\frac{Total\hspace{3}distance}{Total\hspace{3}time}   (1)

Basically the car cover the same distance "d" two times, but at different speeds, so:

Total\hspace{3}distance=2*d

and the total time would be the time t1 required to go from A to B plus the time t2 required to go back from B to A:

Total\hspace{3}time=t1+t2

From basic physics we know:

t=\frac{d}{S1}

so:

t1=\frac{d}{S1}

t2=\frac{d}{S2}

Using the previous information in equation (1)

S_a_v_e_r_a_g_e=\frac{2*d}{\frac{d}{S1} +\frac{d}{S2} }=\frac{2*d}{\frac{d*S2+d*S1}{S1+S2} }

Factoring:

S_a_v_e_r_a_g_e=\frac{2*S1*S2}{S1+S2}   (2)

Finally, replacing the data in (2)

S_a_v_e_r_a_g_e=\frac{2*40*60}{60+40} =48km/h

You might be interested in
Kevin is refinishing his rusty wheelbarrow. He moves his sandpaper back and forth 45 times over a rusty area, each time moving a
dmitriy555 [2]
W = _|....F*dx*cos(a)........With F=force, x=distance over which force acts on object,
.......0.............................and a=angle between force and direction of travel.

Since the force is constant in this case we don't need the equation to be an integral expression, and since the force in question - the force of friction - is always precisely opposite the direction of travel (which makes (a) equal to 180 deg, and cos(a) equal to -1) the equation can be rewritted like so:

W = F*x*(-1) ............ or ............. W = -F*x

The force of friction is given by the equation: Ffriction = Fnormal*(coeff of friction)

Also, note that the total work is the sum of all 45 passes by the sandpaper. So our final equation, when Ffriction is substituted, is:

W = (-45)(Fnormal)(coeff of friction)(distance)
W = (-45)...(1.8N).........(0.92).........(0.15m)
W = ................-11.178 Joules
5 0
3 years ago
A proton is 0.9 meters away from a 1.4 C charge. What is the magnitude of the electric force between the proton and the charge
Digiron [165]

Answer:

F = 2.49 x 10⁻⁹ N

Explanation:

The electrostatic force between two charged bodies is given by Colomb's Law:

F = \frac{kq_1q_2}{r^2}\\

where,

F = Electrostatic Force = ?

k = colomb's constant = 9 x 10⁹ N.m²/C²

q₁ = charge on proton = 1.6 x 10⁻¹⁹ C

q₂ = second charge = 1.4 C

r = distace between charges = 0.9 m

Therefore,

F = \frac{(9\ x\ 10^9\ N.m^2/C^2)(1.6\ x\ 10^{-19}\ C)(1.4\ C)}{(0.9\ m)^2}

<u>F = 2.49 x 10⁻⁹ N</u>

8 0
3 years ago
Read 2 more answers
In the 19th century James Joule, an English scientist, was the first to recognize the mechanical equivalent of heat as a specifi
Dmitry [639]

Answer:

D) wood rubbed against a rough surface feels hot

Explanation:

The heat is transferred from one form of energy (friction of the wood being rubbed against the surface) to another (heat energy).

6 0
3 years ago
Read 2 more answers
I need help plzzzz!!!!!!!!!!!!!!!!
elena-s [515]

Answer:

You were a freeloader of my questions, so I'll be one too.

4 0
3 years ago
True or False:
bekas [8.4K]
I think it false. Sorry if i'm wrong.

5 0
3 years ago
Read 2 more answers
Other questions:
  • What is the definition of uniform motion?
    6·1 answer
  • What type of pipe wrenches are designed for turning and holding where marring is not objectionable?
    12·1 answer
  • At a certain time a particle had a speed of 17 m/s in the positive x direction, and 3.0 s later its speed was 28 m/s in the oppo
    11·1 answer
  • When a star goes from the main sequence to the red giant phase, it becomes larger rather than smaller. This is true because grav
    7·1 answer
  • A black hole in the universe is a An empty region in space b- A massive collapsed star c- A moon that is always turned to its da
    6·1 answer
  • People have proposed driving motors with the earth's magnetic field. This is possible in principle, but the small field means th
    8·1 answer
  • A ball rotates on a string as shown below.
    8·1 answer
  • Can someone pls help me with this
    11·1 answer
  • A driver of a car traveling at 25 m/s applies the brake, causing a uniform acceleration of -3 m/s2. A) How long does it take the
    15·1 answer
  • Two formats of sources are
    11·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!