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3 years ago

10

a 70 kg desk sits on the floor motionless If gravity is pulling it with an acceleration of 9.8 m/s/s how much force is gravity e

xercising on the desk

1 answer:

adell [148]3 years ago

3 0

Since force is mass*acceleration,

F = 70kg * 9.8 m/s

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A 5-g lead bullet traveling in 20°C air at 300 m/s strikes a flat steel plate and stops.

densk [106]

To solve this problem it is necessary to apply the concepts related to the Kinetic Energy and the Energy Produced by the heat loss. In mathematical terms kinetic energy can be described as:

$KE = \frac{1}{2} mv^2$

Where,

m = Mass

v = Velocity

Replacing we have that the Total Kinetic Energy is

$KE = \frac{1}{2} mv^2$

$KE = \frac{1}{2} (5*10^{-3})(300)^2$

$KE = 225J$

On the other hand the required Energy to heat up t melting point is

$Q_1 = mC_p \Delta T$

$Q_2 = L_f m$

Where,

m = Mass

$C_p =$ Specific Heat

$\Delta T =$ Change at temperature

$L_f =$ Latent heat of fussion

Heat required to heat up to melting point,

$Q = Q_1+Q_2$

$Q = mC_p \Delta T+L_f m$

$Q = 5*0.128*(327-20) + 5*24.7$

$Q = 310J$

The energy required to melt is larger than the kinetic energy. Therefore the heat of fusion of lead would be 327 ° C: The melting point of lead.

4 0

3 years ago

A centripetal force causes circular motion because it accelerates an object

MAVERICK [17]

The answer is option A.

Centripetal force is always directed towards the centre and does not change the speed of the body,but there is a change in the direction.

6 0

3 years ago

Read 2 more answers

A baseball of mass 300-g is hit at a velocity of 40 m/s. If the ball is caught by the third baseman and the ball penetrates 2.0

OlgaM077 [116]

The force is -12,000 N

Explanation:

First of all, we calculate the acceleration of the ball, by using the following suvat equation:

$v^2-u^2=2as$

where:

v = 0 is the final velocity of the baseball (it comes to rest)

u = 40 m/s is the initial velocity

a is the acceleration

s = 2.0 cm = 0.02 m is the displacement of the ball

Solving for a,

$a=\frac{v^2-u^2}{2s}=\frac{0-40^2}{2(0.02)}=-40,000 m/s^2$

Now we can calculate the average force exerted on the ball, by using Newton's second law:

$F=ma$

where

m = 300 g = 0.3 kg is the mass of the ball

$a=-40,000 m/s^2$ is the acceleration

Substituting,

$F=(0.3)(-40,000)=-12,000 N$

where the negative sign indicates that the direction of the force is opposite to the direction of motion of the ball.

Learn more about forces:

brainly.com/question/8459017

brainly.com/question/11292757

brainly.com/question/12978926

#LearnwithBrainly

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2 years ago

What is the density of a 15g block of metal with a volume of 2cm3?

JulsSmile [24]

Answer:

density =mass/volume

Explanation:

density=15/2

density=7.5 g/cm³

4 0

3 years ago

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Two carts undergo an inelastic collision where they stick together. Cart A has an initial velocity v0, and the second cart B is

dimulka [17.4K]

Answer:

Explanation:

Initial kinetic energy of the system = 1/2 mA v0²

If Vf be the final velocity of both the carts

applying conservation of momentum

final velocity

Vf = mAvo / ( mA +mB)

kinetic energy ( final ) = 1/2 (mA +mB)mA²vo² / ( mA +mB)²

= mA²vo² / 2( mA +mB)

Given 1/2 mA v0² / mA²vo² / 2( mA +mB) = 6

mA v0² x ( mA +mB) / mA²vo² = 6

( mA +mB) / mA = 6

mA + mB = 6 mA

5 mA = mB

mB / mA = 5 .

3 0

3 years ago