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Andrei [34K]
3 years ago
15

"two planets have the same mass, but planet a has 3 times the radius of planet

Physics
1 answer:
lyudmila [28]3 years ago
4 0
The gravitational acceleration on the surface of planet A is:
g_A =  \frac{GM_A}{r_A^2}
where G is the gravitational constant, M_A is the mass of planet A and r_A its radius.

Similarly, the gravitational acceleration on the surface of planet B is:
g_B = \frac{GM_B}{r_B^2}

The ratio between the gravitational acceleration on planet A and B becomes:
\frac{g_A}{g_B}= \frac{GM_A / r_A^2}{GM_B/r_B^2}  = \frac{M_A r_B^2}{M_B r_A^2}

The problem says that the two masses are equal: M_A = M_B while planet A has 3 times the radius of planet B: r_A = 3 r_B. Substituting into the ratio, we get:
\frac{g_A}{g_B} =  \frac{M_B r_B^2}{M_B (3 r_B)^2} =  \frac{1}{9}

so, gravity on planet B is 9 times stronger than planet A.
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A person is trying to lift a crate that has a mass of 30 kg. The normal force of the floor is currently supplying 150N of force.
alexdok [17]

Here when an object is placed on the level floor then in that case there are two forces on the object

1). Weight of object downwards (mg)

2). Normal force due to floor which will counterbalance the weight (N)

so when no force is applied on the box at that time normal force is counter balanced by weight.

Now here it is given that A person tried to lift the box upwards

So now there are two forces on the box

1). Applied force of person

2). Normal force due to ground

So now these two forces will counter balance the weight of the crate

So we can write an equation for force balance like

F_g = F_n + F_a

given that

F_g = mg

here

m = 30 kg and

g = acceleration due to gravity = 10 m/s^2

F_n = 150 N

now from above equation

30*10 = 150 + F_a

F_a = 300 - 150 = 150 N

So force applied by the person must be 150 N

7 0
3 years ago
In a second experiment, you decide to connect a string which has length L from a pivot to the side of block A (which has width d
Salsk061 [2.6K]

Answer:

The answer is in the explanation

Explanation:

A)

i) The blocks will come to rest when all their initial kinetic energy is dissipated by the friction force acting on them. Since block A has higher initial kinetic energy, on account of having larger mass, therefore one can argue that block A will go farther befoe coming to rest.

ii) The force on friction acting on the blocks is proportional to their mass, since mass of block B is less than block A, the force of friction acting on block B is also less. Hence, one might argue that block B will go farther along the table before coming to rest.

B) The equation of motion for block A is

m_{A}\frac{\mathrm{d} v}{\mathrm{d} t} = -m_{A}g\nu_{s}\Rightarrow \frac{\mathrm{d} v}{\mathrm{d} t} = -\nu_{s}g \quad (1)

Here, \nu_{s} is the coefficient of friction between the block and the surface of the table. Equation (1) can be easily integrated to get

v(t) = C-\nu_{s}gt \quad (2)

Here, C is the constant of integration, which can be determined by using the initial condition

v(t=0) = v_{0}\Rightarrow C = v_{0} \quad (3)

Hence

v(t) = v_{0} - \nu_{s}gt \quad (4)

Block A will stop when its velocity will become zero,i.e

0 = v_{0}-\nu_{s}gT\Rightarrow T = \frac{v_{0}}{\nu_{s}g} \quad (5)

Going back to equation (4), we can write it as

\frac{\mathrm{d} x}{\mathrm{d} t} = v_{0}-\nu_{s}gt\Rightarrow x(t) = v_{0}t-\nu_{s}g\frac{t^{2}}{2}+D \quad (6)

Here, x(t) is the distance travelled by the block and D is again a constant of integration which can be determined by imposing the initial condition

x(t=0) = 0\Rightarrow D = 0 \quad (7)

The distance travelled by block A before stopping is

x(t=T) = v_{0}T-\nu_{s}g\frac{T^{2}}{2} = v_{0}\frac{v_{0}}{\nu_{s}g}-\nu_{s}g\frac{v_{0}^{2}}{2\nu_{s}^{2}g^{2}} = \frac{v_{0}^{2}}{2\nu_{s}g} \quad (8)

C) We can see that the expression for the distance travelled for block A is independent of its mass, therefore if we do the calculation for block B we will get the same result. Hence the reasoning for Student A and Student B are both correct, the effect of having larger initial energy due to larger mass is cancelled out by the effect of larger frictional force due to larger mass.

D)

i) The block A is moving in a circle of radius L+\frac{d}{2} , centered at the pivot, this is the distance of pivot from the center of mass of the block (assuming the block has uniform mass density). Because of circular motion there must be a centripetal force acting on the block in the radial direction, that must be provided by the tension in the string. Hence

T = \frac{m_{A}v^{2}}{L+\frac{d}{2}} \quad (9)

The speed of the block decreases with time due to friction, hence the speed of the block is maximum at the beginning of the motion, therfore the maximum tension is

T_{max} = \frac{m_{A}v_{0}^{2}}{L+\frac{d}{2}} \quad (10)

ii) The forces acting on the block are

a) Tension: Acting in the radially inwards direction, hence it is always perpendicular to the velocity of the block, therefore it does not change the speed of the block.

b) Friction: Acting tangentially, in the direction opposite to the velocity of the block at any given time, therefore it decreases the speed of the block.

The speed decreases linearly with time in the same manner as derived in part (C), using the expression for tension in part (D)(i) we can see that the tension in the string also decreases with time (in a quadratic manner to be specific).

8 0
3 years ago
Why are a 12 ounce hard seltzer and 1.5 ounces of liquor both standard drinks? alchohol edu
Mars2501 [29]

12 ounce hard seltzer and 1.5 ounces of liquor are standard drinks because they contain the <u>same amount</u><u> </u><u>of </u><u>pure alcohol</u>

<h3>What is standard drink?</h3>

This is  a term used to refer to the measure of alcoholic content of drinks  such that the drink should have 14 grams of pure alcohol or 0.6 fluid ounces of pure alcohol. This concept of standard drink is applicable in the United States of America.

The equivalence of a standard drink is 5 percent alcohol as seen in regular beer, 12 percent as seen in wines, and 40 percent as seen in distilled spirits. This measurement in taken by the percentage of the total volume of the beverage. hence the quantity of the drink or beverage may be different as the percentage is what determines the amount of alcohol present

From standard drink chart both drinks has same amount of pure alcohol so they are said to be standard drinks

Read more on standard drinks here: brainly.com/question/17645986

#SPJ1

6 0
1 year ago
Suppose your hair grows at the rate 1/31 in. per day. find the rate at which it grows in nanometers per second. because the dist
kati45 [8]
Hair grows at rate of 9.20nm/s.
7 0
3 years ago
A rocket is fired at 100 m/s at an angle of 37, what was its speed at the top of its path?
Nadusha1986 [10]

Answer:

0m/s

Explanation:

Since its fired at an angle, at the top there will be a split second where the velocity will be 0, as it has a parabolic shape, so the speed at the top of its path is 0

4 0
2 years ago
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