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4 years ago

A 47.4 kg student runs down the sidewalk and jumps with a horizontal speed of 42 m/s onto a stationary skateboard

Physics

1 answer:

Tpy6a [65]4 years ago

8 0

Answer:

3 kg

Explanation:

Momentum before = momentum after

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

After jumping on the skateboard, the student and the skateboard have the same velocity, so v₁ = v₂.

m₁u₁ + m₂u₂ = (m₁ + m₂) v

(47.4 kg) (4.2 m/s) + m (0 m/s) = (47.4 kg + m) (3.95 m/s)

m = 3 kg

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Complete each statement about the sign of the work done on a baseball. Carlton catches a baseball and his hand moves backward as

dezoksy [38]

Answer and Explanation:

The work done is negative as the force is applied in the forward direction and the displacement of the hand is in the backward direction.
The work done is positive as the work is done on the baseball by Carlton. Moreover, both the force applied and the displacement of Carlton are in a straight line in the forward direction.
The work done in this case is zero as Carlton rides with constant speed, the Kinetic energy too remains constant and hence net work done is zero.
The work done in this case is positive as the work is done on the baseball by Carlton and as the velocity changes its Kinetic energy also varies wit it.
Also the force applied and the displacement of Carlton in this case are in the directed to the same path.

8 0

3 years ago

What is the sound intensity level in decibels? Use the usual reference level of I0 = 1.0×10−12 W/m2.

jek_recluse [69]

Answer:

L = 130 decibels

Explanation:

The computation of the sound intensity level in decibels is shown below:

According to the question, data provided is as follows

I = sound intensity = 10 W/m^2

I0 = reference level = $1 \times 10-12 W/m^2$

Now

Intensity level ( or Loudness)is

$L = log10 \frac{I}{10}$

$L = log10 \frac{10}{1\times 10^{-12}}$

$L = log10 \times 1013$

$= 13 \times 1 ( log10(10) = 1)$

Therefore

L = 13 bel

And as we know that

1 bel = 10 decibels

So,

The Sound intensity level is

L = 130 decibels

5 0

4 years ago

What force is needed to accelerate a 1,000-kilogram car from a stop to 5 m/s/s?

solong [7]

That depends on how soon you want it to reach 5 m/s/s. Without friction, ANY force will accelerate the car, like a mosquito pushing on it, but a Space Shuttle booster will accelerate it at a greater rate.

3 0

3 years ago

Does the size of the magnetic field change with the size of the magnet?

mestny [16]

Answer:

Not all of the time, it can also depend on the strength of the magnet.

Explanation:

say you have a small very strong magnet, that might work just as well as a large but week magnet.

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3 years ago

Ninas measurements shown in the table here BEST represent a wave with

Finger [1]

They best represent a wave with zero energy and zero amplitude.

There are no measurements shown in a table that accompanies
this question having any amplitude or energy greater than zero.

3 0

3 years ago

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