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kirill115 [55]
3 years ago
8

A tennis ball is moving at a velocity of +54 m/s before a tennis player returns it with a velocity of -58 m/s. If the ball was i

n contact with her racket for 0.8 s, what was its acceleration? (Assume the acceleration was constant throughout the hit.)
A. -140 m/s2
B. -5 m/s2
C. 72.5 m/s2
D. 112 m/s2
Physics
2 answers:
Tanzania [10]3 years ago
8 0

Answer:

a. 140 m/s2

Explanation:

melomori [17]3 years ago
3 0

Acceleration = (change in speed) / (time for the change)

Change in speed = (speed at the end) minus (speed at the beginning)

Change in speed = (-58 m/s) minus (54 m/s)

Change on speed = -112 m/s

Acceleration = (-112 m/s) / (0.8 s)

Acceleration = -140 m/s²

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(11%) Problem 5: A submarine is stranded on the bottom of the ocean with its hatch 25 m below the surface. In this problem, assu
V125BC [204]

Answer:

F = 1.24*10^4 N

Explanation:

Given

Depth of the ship, h = 25 m

Density of water, ρ = 1.03*10^3 kg/m³

Diameter of the hatch, d = 0.25 m

Pressure of air, P(air) = 1 atm

Pressure of water =

P(w) = ρgh

P(w) = 1.03*10^3 * 9.8 * 25

P(w) = 2.52*10^5 N/m²

P(net) = P(w) + P(air) - P(air)

P(net) = P(w)

P(net) = 2.52*10^5 N/m²

Remember,

Pressure = Force / Area, so

Force = Area * Pressure

Area = πr² = πd²/4

Area = 3.142 * 0.25²/4

Area = 3.142 * 0.015625

Area = 0.0491 m²

Force = 0.0491 * 2.52*10^5

F = 12373 N

F = 1.24*10^4 N

5 0
4 years ago
Read 2 more answers
An object is dropped from rest from a 70.6 m tower. Air resistance is negligible. After 0.32 seconds, what is magnitude and dire
dem82 [27]

Answer:

<em>1,378.9ms²</em>

Explanation:

Given the following

Distance S = 70.6m

Time t = 0.32secs

Initial velocity = 0m/s

Required

Acceleration

Using the equation of motion

S = ut+1/2at²

Substitute

70.6 = 0+1/2a(0.32)²

70.6 = 0.0512a

a = 70.6/0.0512

a = 1,378.9

<em>Hence the acceleration is 1,378.9ms²</em>

7 0
3 years ago
Hanging from a horizontal beam are nine simple pendulums of the following lengths:
LenaWriter [7]

Answer:

Options d and e

Explanation:

The pendulum which will be set in motion are those which their natural frequency is equal to the frequency of oscillation of the beam.

We can get the length of the pendulums likely to oscillate with the formula;

L =\frac{g}{w^{2} }

where g=9.8m/s

         ω= 2rad/s to 4rad/sec

when ω= 2rad/sec

L= \frac{9.8}{2^{2} }

L = 2.45m

when  ω= 4rad/sec

L=\frac{9.8}{4^{2} }

L = 9.8/16

L=0.6125m

L is between 0.6125m and 2.45m.

This means only pendulum lengths in this range will oscillate.Therefore pendulums with length 0.8m and 1.2m will be strongly set in motion.

Have a great day ahead

8 0
4 years ago
1. When an object's distance from another object is changing it must be
slega [8]
An object is in motion if its distance from another object is changing. An object is in motion if it changes position relative to a reference point. An reference point is a place or object used for comparison to determine if something is moving.
3 0
4 years ago
Why the efficiency of heat engine is always less than 100%​
valina [46]

Answer:

because some waste heat is always produced produced in a heat engine.

Explanation:

the fraction of heat input that is converted to a net work output is a measure of the performance of the heat engine and is called the thermal efficiency.Since the machine does not contain a source of energy ,nor can it store energy ,from this conversation of energy the power output of machine can never be greater than its input,so efficiency can be less than 100%.

7 0
3 years ago
Read 2 more answers
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