PHYSICS MIDDLE SCHOOL

The initial kinetic energy imparted to a 0.020 kg bullet is 1200 J. (a) Assuming it accelerated down a 1.00 m rifle barrel, estimate the average power delivered to it during
the firing. (b) Neglecting air resistance, find the range of this projectile when it is fired
at an angle such that the range equals the maximum height attained.

Answers

Answer 1

Answer:

Answer:

(a) Power= 207.97 kW

(b) Range= 5768.6 meter

Explanation:

Given,

Mass of bullet, $m=0.02 kg$

Kinetic energy imparted, $K=1200 J$

Length of rifle barrel, $d=1 m$

(a)

Let the speed of bullet when it leaves the barrel is $v$ .

Kinetic energy, $K=(1)/(2) mv^(2)$

$v=\sqrt{(2K)/(m) }$

$=\sqrt{(2*1200)/(0.02) }$

$=346.4m/s$

Initial speed of bullet, $u=0$

The average speed in the barrel, $v_a_v_g=(u+v)/(2)$

$=(0+346.4)/(2) \n=173.2 m/s$

Time taken by bullet to cross the barrel, $t=(d)/(v)$

$=(1)/(173.2)\n =0.00577 second$

Power, $P_a_v_g=(W)/(t)$

$=(1200)/(0.00577) \n=207.97kW$

(b)

In projectile motion,

Maximum height, $H_m=(v^2\sin^2\theta)/(2g) \n$

Range, $R=(v^2\sin2\theta)/(g)$

given that, $H_m=R$

then, $(v^2\sin^2\theta)/(2g)=(v^2\sin2\theta)/(g)\n\sin^2\theta=2\sin\theta\cos\theta\n\n\tan\theta=4\n\theta=\tan^-^14\n\theta=75.96^0\nR=(v^2\sin2\theta)/(g)\n=(346.4^2*\sin(2*75.96))/(9.8)\n5768.6 meter$

Answer:50 $ms^(-1)$

Explanation:

Let $v_(a)$ be the airspeed.

Let $v_(w)$ be the cross wind speed.

We know that,ground speed is the vector sum of airspeed and cross wind speed and airspeed is perpendicular to cross wind speed.

If $v_(1)$ and $v_(2)$ are two perpendicular vectors,the resultant vector has the magnitude $\sqrt{|v|_(1)^(2)+|v|_(2)^(2)}$

Given,

$v_(a)=40ms^(-1)\nv_(c)=30ms^(-1)$

So,the ground speed is $\sqrt{40^(2)+30^(2)}=√(2500)=50ms^(-1)$

Do you hear sound as soon as it's made? explain?

Answers

No you don't. After the sound is made, it has to travel
to your ears before you can hear it.

The speed of sound in air is about 340 meters per second.
That's about 760 miles per hour. That sounds awfully fast, but
it means that it takes sound almost 5 seconds to cover 1 mile.

Sometimes when you're outside, you might see a neighbor
down the street doing some carpentry outside his house, or
you may see some workers putting a new roof on a house nearby.
If you have this opportunity, watch their hammers carefully.

Light travels much much much much much faster than sound ...
about 874 thousand times as fast as sound. So you see things
just about as soon as they happen, but it takes the sound a while
to reach you. If the distance is about 34 meters (about 110 feet)
or more, then you can start to see the difference ... you'll see the
hammer hit, and then you'll hear it. The farther the distance is,
the longer the delay is.

The same thing happens at a baseball game when the batter
connects. Firstyou see the ball hit the bat and fly away, and
thenyou hear the CRACK !

According to the law of refraction, light passing from air into a piece of glass at an angle of 30 degrees will cause the light to

Answers

Answer:

bend toward the normal line

Explanation:

When light passes from a less dense to a more dense substance, (for example passing from air into water), the light is refracted (or bent) towards the normal. In your question the light is moving from rarer to denser medium

Final answer:

Upon refracting from air to glass, light will bend towards the normal line, reducing the angle of incidence due to the principle of Snell's Law, which governs how light refracts between media. However, the exact refracted angle cannot be determined without the refractive indices of air and glass.

Explanation:

According to the Law of Refraction, also known as Snell's Law, light changes direction when it passes from one medium to another due to a change in speed, which is determined by the mediums' refractive indices. When light passes from air (a medium with a lower refractive index) into glass (a medium with a higher refractive index), it bends towards the normal line, the imaginary line perpendicular to the surface at the point of incidence.

Given that the angle of incidence is 30 degrees, following the formula of Snell's law: n₁ sin θ₁ = n₂ sin θ₂ where n₁ and n₂ are the refractive indices of air and glass, and θ₁ and θ₂ are the angles of incidence and refraction, we could solve for θ₂ which will be the angle of refraction in glass. However without information of refractive indices of air and glass, an exact angle cannot be determined.

In summary, the light ray will bend towards the normal upon entering the glass, hence decreasing the angle of incidence, according to the Law of Refraction or Snell's Law.