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3 years ago

Why should a tennis player "swing through" when hitting a tennis ball?

1 answer:

7 0

If a tennis player does not swing through, meaning they stop swinging the moment they make contact with the ball, they would lose the majority of their power. The momentum that they had built up during the swing is lost the moment they stop swinging, meaning that the ball is hit with a low amount of power.

If the tennis player swings through the whole time they hit the ball, then they keep their momentum as they hit the ball. There is a much higher power level when swinging through than if you were to stop your swing when you hit the ball.

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A 50 Kg box sits at rest on a 30 degree ramp where the coef of static friction is 0.5773. If your push was directed at an angle

emmasim [6.3K]

Given data:

m= 50 Kg,

W= m×g = 50 × 9.81 = 490.5 N

ramp angle (α) = 30 degrees,

coefficient of friction (μs) = 0.5773,

Push at an angle (Θ) = 40 degrees,

Determine: Push to get box move up (P)=?

From the figure,

Resolving the forces along the plane

W sinα + μs.R = P cos Θ --------------------- (i)

Resolving the forces perpendicular to the inclined plane

W cosα = R+Psin Θ => R= W cosα - Psin Θ -------------- (ii)

Solving (i) and (ii) and keeping μs = tan Φ, Φ = Θ 

Pmin = W sin( α +Θ )

= W[ sin α.Cos Θ + cos α.sin Θ]

= 490.5 [ (sin 30.cos40) + (cos30.sin 40)]

= 460.9 N

Minimum push required to move the box up the ramp is 460.9 N

7 0

3 years ago

Which one of the following statements concerning the Stefan-Boltzmann equation is correct? The equation can be used to calculate

Helen [10]

"The equation can be used to calculate the power absorbed by any surface" statement concerning the Stefan-Boltzmann equation is correct.

Answer: Option A

Explanation:

According to Stefan Boltzmann equation, the power radiated by black body radiation source is directly proportionate to the fourth power of temperature of the source. So the radiation transferred is absorbed by another surface and that absorbed power will also be equal to the fourth power of the temperature. So the equation describes the relation of net radiation loss with the change in temperature from hotter temperature to cooler temperature surface.

$P=e \sigma A\left(T^{4}-T_{c}^{4}\right)$

So this law is application for calculating power absorbed by any surface.

4 0

3 years ago

A physics student stands on a cliff overlooking a lake and decides to throw a softball to her friends in the water below. She th

Andre45 [30]

The horizontal distance covered by the ball before hitting the water is 70.4 m

Explanation:

The motion of the ball is the motion of a projectile, so it consists of two independent motions:

A uniform motion along the horizontal (x) direction
A uniformly accelerated motion along the vertical (y) direction

We start by calculating the time of flight of the ball. This can be done by analyzing the vertical motion. We can use the following suvat equation:

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

where:

s = -16.5 m is the vertical displacement of the ball (it is negative because we take upward as positive direction)

$u_y$ is the initial vertical velocity of the ball, which is given by

$u_y = u sin \theta$

where

u = 23.5 m/s is the initial velocity

$\theta=33.5^{\circ}$ is the angle of projection

Substituting,

$u_y=(23.5)(sin 33.5^{\circ})=13.0 m/s$

$a=g=-9.8 m/s^2$ is the acceleration of gravity, downward

Substituting everything into the equation we get:

$-16.5=13.0t-4.9t^2\\4.9t^2-13.0t-16.5=0$

Solving the equation for t, we find the time of flight of the ball:

t = -0.94 s

t = 3.59 s

We ignore the 1st solution since it is negative, so the ball reaches the water after 3.59 seconds.

Now we analyze the horizontal motion of the ball. The horizontal velocity is constant and it is:

$v_x=u cos \theta=(23.5)(cos 33.5^{\circ})=19.6 m/s$

Therefore, the horizontal distance covered in a time t is

$d=v_x t$

And substituting t = 3.59 s, we find

$d=(19.6)(3.59)=70.4 m$

So, the horizontal distance covered by the ball before hitting the water is 70.4 m.

Learn more about projectile motion:

brainly.com/question/8751410

#LearnwithBrainly

4 0

3 years ago

Calculate the momentum of a 4 kg Bolling ball being thrown at a speed of 3 m/s

bonufazy [111]

We are given –

Mass of boiling ball is, m = 4 kg
Speed is, v = 3 m/s
Momentum, P =?

As we know –

↠Momentum = Mass × Speed(Velocity)

↠Momentum = 4 × 3 kgm/s

↠Momentum = 12 kgm/s

Henceforth,Momentum will be 12 kgm/s.

7 0

2 years ago

An object will be stable if __________.

ryzh [129]

Answer:b

Explanation:

Object will be stable if its center of gravity lies over its base of support.

If the center of gravity is above the center of buoyancy then it provides positive righting moment and the object floats over the liquid and such object is said to possess positive meta-centric height.

6 0

3 years ago

Read 2 more answers

Why should a tennis player "swing through" when hitting a tennis ball?​

Why should a tennis player "swing through" when hitting a tennis ball?