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r-ruslan [8.4K]

3 years ago

15

When serving a tennis ball, a player hits the ball when its velocity is zero (at the highest point of a vertical toss). The racq

uet exerts a force of 540 N on the ball for 5.00 ms, giving it a final velocity of 45.0 m/s. Using these data, find the mass (in grams) of the ball.

1 answer:

never [62]3 years ago

7 0

Answer:

60 grams

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

m = Mass

F = Force

Impulse

$J=Ft$

$J=m(v-u)\\\Rightarrow Ft=m(v-u)\\\Rightarrow m=\frac{Ft}{v-u}\\\Rightarrow m=\frac{540\times 5\times 10^{-3}}{45-0}\\\Rightarrow m=0.06\ kg=60\ g$

Mass of the tennis ball is 60 grams

or

$v=u+at\\\Rightarrow a=\frac{v-u}{t}\\\Rightarrow a=\frac{45-0}{0.005}\\\Rightarrow a=9000\ m/s^2$

$F=ma\\\Rightarrow m=\frac{F}{a}\\\Rightarrow m=\frac{540}{9000}\\\Rightarrow m=60\ grams$

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A box (m = 20 kg) is sliding on a horizontal surface. it is connected to a massless hook by a light string passing over a massle

Varvara68 [4.7K]

mass of the box = 20 kg

force of friction on the box due to surface

$F_s = \mu_s N$

$F_s = 0.80 * 20 * 9.8$

$F_s = 156.8 N$

similarly kinetic friction on it

$F_k = \mu_k N$

$F_k = 0.30* 20 * 9.8$

$F_k = 58.8 N$

now the weight of the suspended block will be

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so here the weight of the suspended block is less than the limiting friction on it

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5 0

4 years ago

In a 5000 m race, the athletes run 12 1/2 laps; each lap is 400 m.Kara runs the race at a constant pace and finishes in 17.9 min

Ksju [112]

Answer:

No. of laps of Hannah are 7 (approx).

Solution:

According to the question:

The total distance to be covered, D = 5000 m

The distance for each lap, x = 400 m

Time taken by Kara, $t_{K} = 17.9 min = 17.9\times 60 = 1074 s$

Time taken by Hannah, $t_{H} = 15.3 min = 15.3\times 60 = 918 s$

Now, the speed of Kara and Hannah can be calculated respectively as:

$v_{K} = \frac{D}{t_{K}} = \frac{5000}{1074} = 4.65 m/s$

$v_{H} = \frac{D}{t_{H}} = \frac{5000}{918} = 5.45 m/s$

Time taken in each lap is given by:

$(v_{H} - v_{K})t = x$

$(5.45 - 4.65)\times t = 400$

$t = \frac{400}{0.8}$

t = 500 s

So, Distance covered by Hannah in 't' sec is given by:

$d_{H} = v_{H}\times t$

$d_{H} = 5.45\times 500 = 2725 m$

No. of laps taken by Hannah when she passes Kara:

$n_{H} = \frac{d_{H}}{x}$

$n_{H} = \frac{2725}{400} = 6.8$ ≈ 7 laps

3 0

3 years ago

A person applies a rightward force of 80 N to a cart of physics textbooks what is the reaction force

Goryan [66]

Just as Prof. Newton said: "For every action, there is an EQUAL, OPPOSITE reaction.". (See his motion law #3.)

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3 years ago

You are on an airplane traveling 30° south of due west at 180 m/s with respect to the air. The air is moving with a speed 31 m/s

BlackZzzverrR [31]

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6 0

4 years ago

A block of mass m 5.00 kg is

vekshin1

<span>a.
the force in the direction of movement
Fx = F x cosA*
Fx = 12 x cos25*
Fx = 10.88
m x a = 10.88
a = 10.88/5
a= 2.18 m/s^2
b.
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Fy = mg
Fy = F x sin25*
Fy= 5 x 9.8
Fy= 115.94 N
c.
if Fx = ma
a = 115.94/5
a= 23.19 m/s^2
hope it helps
</span>

6 0

3 years ago