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3 years ago

PLEASE HELP:

1 answer:

7 0

The marble's volume is equal to 1.2 $cm^{3}$
Density= mass/volume
Mass= 3.05 Grams
Volume= 1.2 cm^3
3.05/1.2= 2.92 g/mL

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A bike moves 60 meters in 12 second. calculate the speed of the bike

nikdorinn [45]

Answer:

Speed=Distance

Time

=60

=5m/s

4 0

3 years ago

When does the velocity and speed of a moving body becomes identical?

d1i1m1o1n [39]

The speed and velocity of a moving body become identical when it tends to move in a straight line.

6 0

3 years ago

A force of 400-N pushes on a 25-kg box horizontally. The box accelerates at 9 m/s? Find the coefficient of kinetic friction betw

umka2103 [35]

Answer:

Explanation:

Using the Newtons law of motion;

$\sum Fx = ma_x\\Fm - Ff = ma_x$

Fm is the moving force = 400N

Ff is the frictional force = μR

μ is the coefficient of kinetic friction

R is the reaction = mg

m is the mass

a is the acceleration

The equation becomes;

$Fm - \mu R = ma_x\\Fm - \mu mg = ma_x\\400- \mu (25)(9.8) = 25(9)\\400 - 254.8 \mu = 225\\- 254.8 \mu = 225 - 400\\- 254.8 \mu = -175\\ \mu = \frac{-175}{- 254.8} \\\mu = 0.69$

Hence the coefficient of kinetic friction between the box and floor is 0.69

7 0

3 years ago

Beatrice and the Elevator Beatrice, a middle school student, is visiting a very tall office building and notices that she feels

ahrayia [7]

Explanation:

The question is not complete, here is the complete question

"Beatrice and the Elevator Beatrice, a middle school student, is visiting a very tall office building and notices that she feels heavier when the elevator car is traveling up and lighter when the elevator car is traveling down. After making these observations, Beatrice comes back to the building and stands on a bathroom scale that measures her weight as she travels up and down in the elevator.

1. . What question is Beatrice trying to answer?

2. What is one variable Beatrice could change in her investigation? What might she figure out if this

variable was changed"

1. Beatrice is trying to observe the influence of the elevator movement on her weight, Hence the question is "will the elevator movement cause her weight to change"

therefore moving upward the reading on the scale will increase

Reading=mg+ma

downward

Reading will reduce

Reading=mg-ma

2. The independent variable is the acceleration due to gravity g=9.81m/s^2

while the dependent variables are

i. The elevators acceleration

ii. Beatrice's mass

6 0

3 years ago

A ball rolls off a desk at a speed of 2 m/s and lands 0.50 seconds later.

Hoochie [10]

Answer:

(a) The ball lands 1 m ahead of the desk's base.

(b) The height of the desk is 1.225 m.

Explanation:

Given:

Initial velocity of the ball is, $u_{0}=2\ m/s$

Time of flight of the ball is, $t=0.50\ s$

(a)

Let the ball fall at a distance of $x$ from the base of the desk and let the height of the desk be $y$ .

The given motion of the ball is a projectile motion that can be divided into 2 mutually perpendicular directions.

Now, considering only the horizontal motion of the ball. The ball not under the influence of any force in the horizontal direction.

Therefore, the distance covered by the ball horizontally is given as:

$x=v_0\times t\\x=2\times 0.50=1\ m$

So, the ball lands 1 m ahead of the desk's base.

(b)

Now, consider only the vertical motion of the ball. The ball is under the influence of gravity.

So, vertical distance can be obtained using Newton's equations of motion.

We use the following equation of motion:

$y-y_0=u_{oy}t+\frac{1}{2}gt^2$

Where,

$y_{0}\rightarrow \textrm{initial vertical position of ball}\\u_{oy}\rightarrow \textrm{initial vertical velocity}\\g\rightarrow \textrm{acceleration due to gravity}\\y\rightarrow \textrm{final position of ball vertically}$

Here, as the ball leaves the desk horizontally, initial velocity is only in the horizontal direction and doesn't have any component in the vertical direction. So, $u_{oy}=0\ m/s$

Plug in $y_0=h,y=0,g=-9.8,u_{oy}=0,t=0.5$ . Solve for $h$ .

$0-h=0+\frac{1}{2}(-9.8)(0.5)^2\\-h=-4.9\times 0.25\\h=1.225\ m$

Therefore, the height of the desk is 1.225 m.

6 0

3 years ago