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3 years ago

what is the average speed of (a) a car that travels 400m in 20s. and (b) an athlete who runs 1500m in 4 minutes

Physics

1 answer:

zmey [24]3 years ago

5 0

Answer:

a) 20 m/s

b) 37.5 m)s

Explanation:

Average speed = total distance ÷ total time

=> (a) average speed of a car that travels 400m in 20s

= 400/20 = 20 m/s

& (b) average speed of an athlete who runs 1500m in 4 minutes (or 4×60=240 seconds)

= 1500/240 = 37.5 m/s

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a radio antenna broadcasts a 1.0 MHz radio wav e with 21 kW of power. Assume that the radiation is emitted uniformly in all dire

My name is Ann [436]

Answer:

$I=2.67\times 10^{-6}\ W/m$

Explanation:

Given that,

Frequency of a radio antenna is 1 MHz

Power, P = 21 kW

We need to find the the waves intensity 25 km from the antenna . The object emits intenisty evenly in all direction. It can be given by :

$I=\dfrac{P}{4\pi r^2}\\\\I=\dfrac{21\times 10^3}{4\pi (25000)^2}\\\\I=2.67\times 10^{-6}\ W/m$

So, the wave intensity 25 km from the antenna is $2.67\times 10^{-6}\ W/m$ .

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3 years ago

what is the energy of an electromagnetic wave that has a frequency of 8.0 x 10^15 Hz? Use the equation...

Katarina [22]

(C)

Explanation:

$E = hf = (6.626×10^{-34}\:\text{J•s})(8.0×10^{15}\:\text{Hz})$

$= 5.3×10^{-18}\:\text{J}$

4 0

2 years ago

Calculate the current passing through a conductor of resistance 4ohms. If a potential difference of 15V its ends______

statuscvo [17]

Explanation:

current = velocity/resistance

I = V/R

15/4

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6 0

2 years ago

The Kentucky Derby is held at the Churchill Downs track in Louisville, Kentucky. The track is one and one-quarter miles in lengt

Lera25 [3.4K]

Answer:

2.815 seconds

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration

$s=ut+\frac{1}{2}at^2\\\Rightarrow 1609.34=16.58\times t+\frac{1}{2}\times 0.0105\times t^2\\\Rightarrow \\\Rightarrow 4.905t^2+16.58t-1609.34=0$

$t=\frac{-16.58+\sqrt{308.69254}}{0.0105},\:t=\frac{-16.58-\sqrt{308.69254}}{0.0105}\\\Rightarrow t=94.25, -3252\ s$

Time taken with the acceleration is 94.25 seconds

Time = Distance / Speed

$\text{Time}=\frac{1609.34}{16.58}\\\Rightarrow \text{Time}=97.065\ s$

Difference in time = 97.065-94.25 = 2.815 seconds

6 0

3 years ago

A 2kg blob of putty moving at 4 m/s slams into a 6kg blob of putty at rest what is the speed of the to stick together blobs imme

andrew11 [14]

<h2>Answer</h2>

1m/s

<h2>Explanation</h2>

Given that:

<em>Mass of first blob = 2kg = m1</em>

<em>Velocity of blob = 4m/s = v1</em>

<em>Mass of second blob = 6kg = m2</em>

<em>Velocity of blob = 0m/s = v2</em>

<em />

To find:

<em>Final velocity = Vf</em>

<em />

<em>This question is of inelastic collision which is any collision between objects in which some energy is lost.</em>

<em />

<h3>Formula to be use:</h3><h2>(m1*v1) + (m2*V2) = Vf(m1 + m2)</h2>

(2*4) + (6*0) = Vf(2+6)

8 + 0 = Vf(8)

8 = Vf(8)

Vf = 1 m/s

So the speed of two blobs immediately after colliding = 1 m/s

3 0

3 years ago

what is the average speed of (a) a car that travels 400m in 20s. and (b) an athlete who runs 1500m in 4 minutes​

what is the average speed of (a) a car that travels 400m in 20s. and (b) an athlete who runs 1500m in 4 minutes