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3 years ago

Erica throws a tennis ball against a wall, and it bounces back. Which force is responsible for sending the ball back to Erica?

Physics

1 answer:

Anna71 [15]3 years ago

8 0

OPTIONS :

A.) the force that the ball exerts on the wall

B.) the frictional force between the wall and the ball

C.) the acceleration of the ball as it approaches the wall

D.) the normal force that the wall exerts on the ball

Answer: D.) the normal force that the wall exerts on the ball

Explanation: The normal force acting on an object can be explained as a force experienced by an object when it comes in contact with a flat surface. The normal force acts perpendicular to the surface of contact.

In the scenario described above, Erica's tennis ball experiences an opposite reaction after hitting the wall.This is in relation to Newton's 3rd law of motion, which states that, For every action, there is an equal and opposite reaction.

The reaction force in this case is the normal force exerted on the ball by the wall perpendicular to the surface of contact.

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If an object is thrown upward with an initial velocity of 128 ft/second, then its height after t seconds is given by the follow

IrinaK [193]

Answer:

The maximum height attained by the object and the number of seconds are 128 ft and 4 sec.

Explanation:

Given that,

Initial velocity u= 128 ft/sec

Equation of height

$h = 128t-32t^2$ ....(I)

(a). We need to calculate the maximum height

Firstly we need to calculate the time

$\dfrac{dh}{dt}=0$

From equation (I)

$\dfrac{dh}{dt}=128-64t$

$128-64t=0$

$t=\dfrac{128}{64}$

$t=2\ sec$

Now, for maximum height

Put the value of t in equation (I)

$h =128\times2-32\times4$

$h=128\ ft$

(b). The number of seconds it takes the object to hit the ground.

We know that, when the object reaches ground the height becomes zero

$128t-32t^2=0$

$t(128-32t)=0$

$128=32t$

$t=4\ sec$

Hence, The maximum height attained by the object and the number of seconds are 128 ft and 4 sec.

3 0

3 years ago

Sam's job at the amusement park is to slow down and bring to a stop the boats in the log ride. If a boat and its riders have a m

shutvik [7]

Answer:

Sam will do 1152 J of work to stop the boat

Explanation:

Work: This is defined as the product of force and distance, the S.I unit of work is Joules. At any point in science, during calculation Energy and worked can be interchange because they have the same unit.

E = W = 1/2mv²................ Equation 1

Where E = energy, W = work, m = mass, v = velocity.

Given: m = 900 kg, v = 1.6 m/s

Substituting these values into equation 1

W = 1/2(900)(1.6)²

W = 450×2.56

W = 1152 J.

Therefore Sam will do 1152 J of work to stop the boat

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4 years ago

Characteristics that a scientific measuring tool should have

bixtya [17]

Answer:

RELIBILITY - is the consistency of your measurement, or the degree to which an

instrument measures the same way each time it is used under the same condition with the

same subjects. In short, it is the repeatability of your measurement. A measure is considered

reliable if a person's score on the same test given twice is similar. It is important to

remember that reliability is not measured, it is estimated. A good instrument will produce

consistent scores. An instrument’s reliability is estimated using a correlation coefficient of

one type or another.

VALIDITY

VALIDITY - Validity is the extent to which a test measures what it claims to measure. It is

vital for a test to be valid in order for the results to be accurately applied and interpreted.

Validity isn’t determined by a single statistic, but by a body of research that demonstrates

the relationship between the test and the behavior it is intended to measure. There are three

types of validity: It is the strength of our conclusions, inferences or propositions. More

formally, Cook and Campbell (1979) define it as the "best available approximation to the

truth or falsity of a given inference, proposition or conclusion."

PRACTICIBILITY

PRACTICIBILITY - It should be feasible & usable. Quality of being usable in context to the

objective to be achieved.

USABILITY

USABILITY(practicality) ease in administration, scoring, interpretation and application, low

cost, proper mechanical make – up

MEASUREABILITY

MEASUREABILITY - It should measure the objective to be achieved.

Explanation:

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