Questions for 1.21 physics lab report

A garage door opener has a power rating of 350 watts. If the door is in operation for 30 seconds, how many joules of energy are

Ksju [112]

Because of the hint we can conclude what equation we need to solve this problem. We have power and duration that means that we need to express energy:

1 joule = 1watt * 1 second
or
E (energy) = P (power) * t (time duration)
E = 350 * 30 = 10500 joules.

7 0

2 years ago

Why does it rain a lot?

Vaselesa [24]

Answer:

Clouds are made up of tiny water droplets. ... As more and more droplets join together they become too heavy and fall from the cloud as rain. Warm air can hold more moisture than cool air. When the warmer air is cooled and the moisture condenses, it often rains more heavily.

Explanation:

hope it helps

3 0

3 years ago

A 58.0-kg projectile is fired at an angle of 30.0° above the horizontal with an initial speed of 140 m/s from the top of a cliff

strojnjashka [21]

(a) $6.43\cdot 10^5 J$

The total mechanical energy of the projectile at the beginning is the sum of the initial kinetic energy (K) and potential energy (U):

$E=K+U$

The initial kinetic energy is:

$K=\frac{1}{2}mv^2$

where m = 58.0 kg is the mass of the projectile and $v=140 m/s$ is the initial speed. Substituting,

$K=\frac{1}{2}(58 kg)(140 m/s)^2=5.68\cdot 10^5 J$

The initial potential energy is given by

$U=mgh$

where g=9.8 m/s^2 is the gravitational acceleration and h=132 m is the height of the cliff. Substituting,

$U=(58.0 kg)(9.8 m/s^2)(132 m)=7.5\cdot 10^4 J$

So, the initial mechanical energy is

$E=K+U=5.68\cdot 10^5 J+7.5\cdot 10^4 J=6.43\cdot 10^5 J$

(b) $-1.67 \cdot 10^5 J$

We need to calculate the total mechanical energy of the projectile when it reaches its maximum height of y=336 m, where it is travelling at a speed of v=99.2 m/s.

The kinetic energy is

$K=\frac{1}{2}(58 kg)(99.2 m/s)^2=2.85\cdot 10^5 J$

while the potential energy is

$U=(58.0 kg)(9.8 m/s^2)(336 m)=1.91\cdot 10^5 J$

So, the mechanical energy is

$E=K+U=2.85\cdot 10^5 J+1.91 \cdot 10^5 J=4.76\cdot 10^5 J$

And the work done by friction is equal to the difference between the initial mechanical energy of the projectile, and the new mechanical energy:

$W=E_f-E_i=4.76\cdot 10^5 J-6.43\cdot 10^5 J=-1.67 \cdot 10^5 J$

And the work is negative because air friction is opposite to the direction of motion of the projectile.

(c) 88.1 m/s

The work done by air friction when the projectile goes down is one and a half times (which means 1.5 times) the work done when it is going up, so:

$W=(1.5)(-1.67\cdot 10^5 J)=-2.51\cdot 10^5 J$

When the projectile hits the ground, its potential energy is zero, because the heigth is zero: h=0, U=0. So, the projectile has only kinetic energy:

E = K

The final mechanical energy of the projectile will be the mechanical energy at the point of maximum height plus the work done by friction:

$E_f = E_h + W=4.76\cdot 10^5 J +(-2.51\cdot 10^5 J)=2.25\cdot 10^5 J$

And this is only kinetic energy:

$E=K=\frac{1}{2}mv^2$

So, we can solve to find the final speed:

$v=\sqrt{\frac{2E}{m}}=\sqrt{\frac{2(2.25\cdot 10^5 J)}{58 kg}}=88.1 m/s$

4 0

3 years ago

If an orange falls off the table, what causes it to stop?

emmasim [6.3K]

The floor or chair absorbing the force of the impact from the orange causes the orange to stop.

7 0

3 years ago

State ohm’s law Q.34.7

defon

Ohm's law states that: $V=RI$

Explanation:

Ohm's law states that in a conductor, the potential difference across the conductor is directly proportional to the current flowing through it. Mathematically,

$V \propto I$

where

V is the potential difference

I is the current

The constant of proportionality is called resistance (R), and it gives a measure of "how much the conductor opposes" to the flow of current. Therefore Ohm's law can be rewritten as

$V=RI$

where R is the resistance. By rewriting the equation as

$I=\frac{V}{R}$

we see that the larger the resistance, the lower the current in the conductor.

Learn more about Ohm's law:

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brainly.com/question/10597501

brainly.com/question/12246020

#LearnwithBrainly

4 0

3 years ago