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3 years ago

15

You travel an an average speed of 20 km/h in a straight line to get to your grandmothers house. It takes you 3 hours to get to h

er house. How far away is her house from where you started?

1 answer:

Ber [7]3 years ago

6 0

20km every 1 hr is what 20km/hr means.

so 3hrs is 20km*3=60km.

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A professor drives off with his car (mass 870 kg), but forgot to take his coffee mug (mass 0.47 kg) off the roof. The coefficien

SSSSS [86.1K]

Answer: $6.86 m/s^2$

Explanation:

Given

mas of car=870 kg

coffee mug mass=0.47 kg

coefficient of static friction between mug and roof $\mu _s= 0.7$

Coefficient of kinetic Friction $\mu _k=0.5$

maximum car acceleration is $\mu \times g$

here coefficient of static friction comes in to action because mug is placed over car . If mug is moving relative to car then \mu _k is come into effect

$a_{max}=0.7\times 9.8=6.86 m/s^2$

8 0

3 years ago

Plz help..During takeoff a plane accelerates at 4m/s^2 and takes 40s to reach takeoff speed.

matrenka [14]

Answer:

The velocity of the plane at take off is 160 m/s.

The distance travel by the plane in that time is 3200 meter.

Explanation:

Given:

Acceleration, a = 4 m/s²

Time, t = 40 s

u = 0 i .e initial velocity

To Find:

velocity , v = ?

distance , s =?

Solution:

we have first Kinematic equation

v = u + at

∴ v = 0 + 4×40

∴ v = 160 m/s

Now by Third Kinematic equation

$s = ut + \frac{1}{2}at^{2}$

∴ s = 0 + 0.5 × 4× 40²

∴ s = 3200 meter

3 0

3 years ago

1. An asphalt block has a mass of 90 kg and a volume of 0.075 m. Determines the density of the asphalt.

Kisachek [45]

Answer:

1. Density = 1200[kg/m^3]; 2. Volume= 0.005775[m^3], mass= 15.59[kg]

Explanation:

1. We know that the density is defined by the following expression.

$Density = \frac{mass}{volume} \\where:\\mass=90[kg]\\volume=0.075[m^{3} ]\\density=\frac{90}{0.075} \\density=1200[\frac{kg}{m^{3} }]$

2. First we need to convert the units to meters.

wide = 35[cm] = 35/100 = 0.35[m]

long = 11 [dm] = 11 decimeters = 11/10 = 1.1[m]

Thick = 15[mm] = 15/1000 = 0.015[m]

Now we can find the density using the expression for the density.

$density= \frac{mass}{volume} \\where:\\volume = wide*long*thick\\volume=0.35*1.1*0.015 = 0.005775[m^3]\\\\mass= density*volume = 2700*0.005775 = 15.59[kg]$

7 0

3 years ago

Suppose a sound wave and an electromagnetic wave have the same frequency. Which has the longer wavelength? 1. the electromagneti

Mashcka [7]

Answer:

1. the electromagnetic wave.

Explanation:

Mathematically,

wavelength = velocity ÷ frequency

A mechanical wave is a wave that is not capable of transmitting its energy through a vacuum. Mechanical waves require a medium in order to transport their energy from one location to another. A sound wave is an example of a mechanical wave. Sound waves are incapable of traveling through a vacuum.

Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter, increasing frequency decreases wavelength.

Sound waves (which obviously travel at the speed of sound) are much slower than electromagnetic waves (which travel at the speed of light.)

Electromagnetic waves are much faster than sound waves and If the Velocity of the wave increases and the frequency is constant, the wavelength also increases.

7 0

3 years ago

A sprinter moving at 10 m/s slows down at a rate of 1.4 m/s2. how fast is the runner moving after 4 seconds?

AURORKA [14]

V=u+at
v=10+(-1.4 (4))
=10-5.6
=4.4m/s

3 0

3 years ago

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