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2 years ago

How many foot-pounds of work does it take to throw a baseball 90 mph? a baseball weighs 5 oz, or 0.3125 lb?

Physics

1 answer:

NARA [144]2 years ago

5 0

Kinetic energy of the ball is (mv²) / 2, where m is the mass and v is the velocity

So plugging in the mass and the velocity into the kinetic energy expression, you get:

Kinetic energy of the ball = (mv²) / 2

(0.3125/32) times (132)² divided by 2 = 85 ft-lbs

Kinetic energy of the ball = 85 ft-lbs

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Referring to the above diagram, how high will the ball rise on the right-hand incline?

Marina CMI [18]

I think it’s 15cm
Might be 7cm

3 0

3 years ago

The time, t, required to drive a fixed distance varies inversely as the speed, r. It takes 3 hr at a speed of 14 km/h to driv

kenny6666 [7]

Answer:

time taken with speed 23 km/h will be 1.8 hours or 1 hour 48 minutes

Explanation:

Given:

Time is inversely proportional to the speed

mathematically,

t ∝ (1/r)

let the proportionality constant be 'k'

thus,

t = k/r

therefore, for case 1

time = 3 hr

speed = 14 km/hr

3 = k/14

also,

for case 2

let the time be = t

r = 23 km/h

thus,

we have

t = k/23

on dividing equation 2 by 1

we get

$\frac{t}{3}=\frac{k/23}{k/14}$

$t=\frac{14\times3}{23}$

t = 1.8 hr = or 1 hour 48 minutes ( 0.8 hours × 60 minutes/hour = 48 minutes)

4 0

2 years ago

Briefly explain the two postulates of relativity, how they differed from classical physics, and why Einstein was led to propose

Ray Of Light [21]

Explanation:

The two postulates of special theory of relativity

Postulate 1: The law of physics are invariant under any of inertial frame of reference.

Postulate 2: The velocity of light is remains same in each ans every frame of reference and independent of relativity.

They are differ from classical mechanics that in classical mechanics there is no change in mass and length in relative velocity but in relativistic mechanics it changes.

These two postulates implements in phenomenon like time dilation , length contraction etc.

Thanks

3 0

3 years ago

A copper wire of resistivity 2.6 × 10-8 Ω m, has a cross sectional area of 35 × 10-4 cm2

KengaRu [80]

Answer:

the length of the wire is 134.62 m.

Explanation:

Given;

resistivity of the copper wire, ρ = 2.6 x 10⁻⁸ Ωm

cross-sectional area of the wire, A = 35 x 10⁻⁴ cm² = ( 35 x 10⁻⁴) x 10⁻⁴ m²

resistance of the wire, R = 10Ω

The length of the wire is calculated as follows;

$R = \frac{\rho L}{A} \\\\L = \frac{RA}{\rho} \\\\L= \frac{10 \times (35\times 10^{-4}) \times 10^{-4}}{2.6 \times 10^{-8}} \\\\L = 134.62 \ m$

Therefore, the length of the wire is 134.62 m.

6 0

2 years ago

A 750-newton person stands in an elevator that isaccelerating downward. The upward force of theelevator floor on the person must

Margaret [11]

(2)<span>less than 750 N.( if the downward acceleration of elevator were g,then answer would be 0 N.)</span>

7 0

2 years ago