Which phrase describes what a scientist does?

A ball is tossed with enough speed straight up so that it is in the air several seconds. (a) What is the velocity of the ball wh

irina1246 [14]

(a) Zero

When the ball reaches its highest point, the direction of motion of the ball reverses (from upward to downward). This means that the velocity is changing sign: this also means that at that moment, the velocity must be zero.

This can be also understood in terms of conservation of energy: when the ball is tossed up, initially it has kinetic energy

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

where m is the ball's mass and v is the initial speed. As it goes up, this kinetic energy is converted into potential energy, and when the ball reaches the highest point, all the kinetic energy has been converted into potential energy:

$U=mgh$

where g is the gravitational acceleration and h is the height of the ball at highest point. At that point, therefore, the potential energy is maximum, while the kinetic energy is zero, and so the velocity is also zero.

(b) 9.8 m/s upward

We can find the velocity of the ball 1 s before reaching its highest point by using the equation:

$a=\frac{v-u}{t}$

where

a = g = -9.8 m/s^2 is the acceleration due to gravity, which is negative since it points downward

v = 0 is the final velocity (at the highest point)

u is the initial velocity

t = 1 s is the time interval

Solving for u, we find

$u=v-at = 0 -(-9.8 m/s^2)(1 s)= +9.8 m/s$

and the positive sign means it points upward.

(c) -9.8 m/s

The change in velocity during the 1-s interval is given by

$\Delta v = v -u$

where

v = 0 is the final velocity (at the highest point)

u = 9.8 m/s is the initial velocity

Substituting, we find

$\Delta v = 0 - (+9.8 m/s)=-9.8 m/s$

(d) 9.8 m/s downward

We can find the velocity of the ball 1 s after reaching its highest point by using again the equation:

$a=\frac{v-u}{t}$

where this time we have

a = g = -9.8 m/s^2 is the acceleration due to gravity, still negative

v is the final velocity (1 s after reaching the highest point)

u = 0 is the initial velocity (at the highest point)

t = 1 s is the time interval

Solving for v, we find

$v = u+at = 0 +(-9.8 m/s^2)(1 s)= -9.8 m/s$

and the negative sign means it points downward.

(e) -9.8 m/s

The change in velocity during the 1-s interval is given by

$\Delta v = v -u$

where here we have

v = -9.8 m/s is the final velocity (1 s after reaching the highest point)

u = 0 is the initial velocity (at the highest point)

Substituting, we find

$\Delta v = -9.8 m/s - 0=-9.8 m/s$

(f) -19.6 m/s

The change in velocity during the overall 2-s interval is given by

$\Delta v = v -u$

where in this case we have:

v = -9.8 m/s is the final velocity (1 s after reaching the highest point)

u = +9.8 m/s is the initial velocity (1 s before reaching the highest point)

Substituting, we find

$\Delta v = -9.8 m/s - (+9.8 m/s)=-19.6 m/s$

(g) -9.8 m/s^2

There is always one force acting on the ball during the motion: the force of gravity, which is given by

$F=mg$

where

m is the mass of the ball

g = -9.8 m/s^2 is the acceleration due to gravity

According to Newton's second law, the resultant of the forces acting on the body is equal to the product of mass and acceleration (a), so

$mg = ma$

which means that the acceleration is

$a= g = -9.8 m/s^2$

and the negative sign means it points downward.

7 0

4 years ago

What is the frequency of this wave?

Reptile [31]

It’s 4 because a coiled springs is closely spaced then widen

3 0

3 years ago

Read 2 more answers

A shopping cart given an initial velocity of 2.0 m/s north undergoes a constant acceleration of 3.0 m/s2 north. what is the dist

morpeh [17]

Following the initial 4.0 seconds of travel, the cart moved 32m.

<h3>What is an equation of motion?</h3>

Physicists use equations of motion to describe how a physical system behaves in terms of how its motion changes over time.

The behavior of a physical system is described by the equations of motion in more detail as a collection of mathematical functions expressed in terms of dynamic variables. These variables typically comprise time and spatial coordinates, but they could also have momentum components. The most flexible option is generalized coordinates, which can be any useful variable that is a component of the physical system. In classical mechanics, the functions are defined in a Euclidean space, while curved spaces are used in relativity instead. The equations are the answers to the differential equations describing the motion of the dynamics of the dynamics of a system are known. The amount of motion changes according to the strength of the force and does so in the direction of the force's applied straight line.

To know more about equations of motion, click here:

brainly.com/question/14355103

#SPJ4

7 0

2 years ago

Light travels 300 000 000 m/s and one year has approximately 32 000 000 second a light year is the distance light travels in one

Lelu [443]

Explanation:

It is given that,

Speed of light, $v=300 000 000\ m/s=3\times 10^8\ m/s$

Seconds in 1 year, $t=32 000 000=32\times 10^6\ s$

We need to find the distance traveled by light in one year. Speed of an object is given by :

$v=\dfrac{d}{t}$

So,

$d=v\times t\\\\d=3\times 10^8\times 32\times 10^6\\\\d=9.6\times 10^{15}\ m$

Since,

$1\ \text{light year}=9.46\times 10^{15}\ m\\\\1\ m=\dfrac{1}{9.46\times 10^{15}}\ \text{ly}\\\\9.6\times 10^{15}\ m=\dfrac{9.6\times 10^{15}}{9.46\times 10^{15}}\\\\d=1.01\ \text{ly}$

So, the distance covered by light is 1.01 light years.

8 0

3 years ago

A car traveling on a level road initially has 440 kJ of mechanical energy. After the brakes are applied for a few seconds, the c

Anvisha [2.4K]

Answer:

Explanation:

Given that

There's a change in friction from 440 kJ to 110 kJ

This change is as a result of conversion of energy. The energy of the car system converted the mechanical energy in it, into a corresponding heat energy. During the course of this conversion, is where a whopping 330 kJ of energy went missing.

The 330 kJ of energy was lost as a result of the conversion of mechanical energy into heat energy by the use of friction.

3 0

3 years ago