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3 years ago

How do stop watches measure to get the accurate measurement?

Physics

1 answer:

solmaris [256]3 years ago

7 0

Answer:

They measure short time intervals of min and sec to an accuracy of +0.1s

Explanation:

pressing the 1st button starts it, and pressing the 2nd button stops it.

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A ball is thrown vertically upward, which is the positive direction. A little later, it returns to its point of release. The bal

Aleks [24]

Answer:

The initial velocity of the ball is <u>39.2 m/s in the upward direction.</u>

Explanation:

Given:

Upward direction is positive. So, downward direction is negative.

Tota time the ball remains in air (t) = 8.0 s

Net displacement of the ball (S) = Final position - Initial position = 0 m

Acceleration of the ball is due to gravity. So, $a=g=-9.8\ m/s^2$ (Acting down)

Now, let the initial velocity be 'u' m/s.

From Newton's equation of motion, we have:

$S=ut+\frac{1}{2}at^2$

Plug in the given values and solve for 'u'. This gives,

$0=8u-0.5\times 9.8\times 8^2\\\\8u=4.9\times 64\\\\u=\frac{4.9\times 64}{8}\\\\u=4.9\times 8=39.2\ m/s$

Therefore, the initial velocity of the ball is 39.2 m/s in the upward direction.

3 0

3 years ago

If 1.8 amp flows through a 40 ohm resistor, the voltage across the resistor is :

GenaCL600 [577]

Answer:

72 volts.

Explanation:

To solve this, we have to use the Ohm's law.

The ohm's law tells us that the voltage drop of a resistor is directly proportional to the current applied to the conductor.

$V=I*R$

in this case the current is 1.8 amps and the resistor is 40 ohm

$V=1.8*40$

$V=72 volts$ .

5 0

3 years ago

A rubber ball is dropped and bounces vertically from a horizontal concrete floor. If the ball has a speed of 3 m/s just before s

Ganezh [65]

Answer:

F=12.5N

Explanation:

Net force = rate of change of momentum

$F = m*a$

so find the change of momentum P

Pdown

$P=m*v_1=0.42kg*3m/s$

Pup

$P=m*v_1=0.42kg*6.5m/s$

dP = change in P

$dP= 0.42kg (3- -.6.5)m/s =3.99 kg m/s$

$dT = 0.32 s$

$F = \frac{dP}{dt}=\frac{3.99Kg*m/s}{0.32s} =12.468 N$

6 0

3 years ago

The electric eye that prevents an elevator door from closing when you are in the doorway relies upon which physics principle?

goblinko [34]

It's Photoelectric Effect, I just a test with this same question. I am not good for explaining exactly how, but I was right.

3 0

3 years ago

Read 2 more answers

A mango falls fromthe top its tree passing a window which is 2.4m tall by taking 0.4s

Natasha2012 [34]

Explanation:

There are three points in time we need to consider. At point 0, the mango begins to fall from the tree. At point 1, the mango reaches the top of the window. At point 2, the mango reaches the bottom of the window.

We are given the following information:

y₁ = 3 m

y₂ = 3 m − 2.4 m = 0.6 m

t₂ − t₁ = 0.4 s

a = -9.8 m/s²

t₀ = 0 s

v₀ = 0 m/s

We need to find y₀.

Use a constant acceleration equation:

y = y₀ + v₀ t + ½ at²

Evaluated at point 1:

3 = y₀ + (0) t₁ + ½ (-9.8) t₁²

3 = y₀ − 4.9 t₁²

Evaluated at point 2:

0.6 = y₀ + (0) t₂ + ½ (-9.8) t₂²

0.6 = y₀ − 4.9 t₂²

Solve for y₀ in the first equation and substitute into the second:

y₀ = 3 + 4.9 t₁²

0.6 = (3 + 4.9 t₁²) − 4.9 t₂²

0 = 2.4 + 4.9 (t₁² − t₂²)

We know t₂ = t₁ + 0.4:

0 = 2.4 + 4.9 (t₁² − (t₁ + 0.4)²)

0 = 2.4 + 4.9 (t₁² − (t₁² + 0.8 t₁ + 0.16))

0 = 2.4 + 4.9 (t₁² − t₁² − 0.8 t₁ − 0.16)

0 = 2.4 + 4.9 (-0.8 t₁ − 0.16)

0 = 2.4 − 3.92 t₁ − 0.784

0 = 1.616 − 3.92 t₁

t₁ = 0.412

Now we can plug this into the original equation and find y₀:

3 = y₀ − 4.9 t₁²

3 = y₀ − 4.9 (0.412)²

3 = y₀ − 0.83

y₀ = 3.83

Rounded to two significant figures, the height of the tree is 3.8 meters.

6 0

3 years ago