I need help!!! What is the answer!!

a football is thrown upward at a 31° angle to the horizontal.the acceleration of gravity is 9.8m/s^2. To throw the ball a distan

mr Goodwill [35]

The ball's vertical position $y$ in the air at time $t$ is

$y=v_0\sin31^\circ\,t-\dfrac g2t^2$

The ball is at its original height when $y=0$ , which happens at

$v_0\sin31^\circ\,t-\dfrac g2t^2=\dfrac t2\left(2v_0\sin31^\circ-gt)=0$

$\implies t=0\text{ and }t=\dfrac{2v_0\sin31^\circ}g$

Meanwhile, the ball's horizontal position $x$ at time $t$ is

$x=v_0\cos31^circ\,t$

So when the ball reaches its original height a second time, the ball will have traveled a horizontal distance of

$x=\dfrac{2{v_0}^2\sin31^\circ\cos31^\circ}g=\dfrac{{v_0}^2\sin(2\cdot31^\circ)}g$

(which you might recognize as the formula for the range of a projectile)

To reach a distance of $x=77\,\rm m$ , the initial speed $v_0$ would be

$77\,\mathrm m=\dfrac{{v_0}^2\sin62^\circ}{9.8\,\frac{\rm m}{\mathrm s^2}}\implies v_0=29\dfrac{\rm m}{\rm s}$

7 0

3 years ago

A worker drives a 0.554 kg spike into a rail tie with a 2.30 kg sledgehammer. The hammer hits the spike with a speed of 62.7 m/s

Goryan [66]

Answer:

Increase in total energy will be equal to the increase in the internal energy i.e $1130.246$ Joules

Explanation:

Given

Weight of sledge hammer $= 2.30$ kilogram

Speed of sledge hammer $= 62.7$ meter per second

Kinetic energy is equal to half the product of mass and velocity square

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

Substituting the value of mass and velocity, we get -

$KE = 0.5 * 2.30 * 62.7^2\\KE = 4520.9835$

It is given that one fourth of the energy is converted into internal energy

One fourth of kinetic energy is equal to

$\frac{1}{4} * 4520.9835\\= 1130.246$

Increase in total energy will be equal to the increase in the internal energy i.e $1130.246$ Joules

8 0

3 years ago

Read 2 more answers

How do you find the voltage of a section of a parallel circuit?

sergiy2304 [10]

Answer: Voltage is the same across each component of the parallel circuit. The sum of the currents through each path is equal to the total current that flows from the source. You can find total resistance in a Parallel circuit with the following formula: 1/Rt = 1/R1 + 1/R2 + 1/R3 +.

Hope this helps!

3 0

3 years ago

Which occurs when a wave is reflected?

dmitriy555 [2]

Answer: The wave can flip upside down.

Reflection is the bending of a wave when it cannot pass through. For example, plain mirrors which are flat, a ray of light hits the mirror and is reflected from the mirror since it cannot pass through

When reflection occurs the speed and frequency of the wave does not change but the wave is flipped upside down.

The speed does not change because speed is affected by the change in medium the frequency also remains the same since the energy of the wave does not change.

3 0

3 years ago

Read 2 more answers

Calculate the angular velocity of a clocks second hand, its minute hand, and its hour hand. State in Rad/s. What is its angular

fenix001 [56]

Second hand:

1 rev per minute = (2π radians/minute) x (1 min/60sec) = π/30 rad/sec

Minute hand:

1 rev per hour = (2π radians/hour) x (1 hr/3600 sec) = π/1800 rad/sec

Hour hand:

1 rev per 12 hours = (2π rad/12 hr) x (1 hr/3600 sec) = π/21,600 rad/sec

As long as the clock is in good working order, and the hands are turning steadily at their normal rate, there is no angular acceleration.

8 0

3 years ago