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kirill115 [55]
3 years ago
9

A sprinter explodes out of the starting block with an acceleration of +4.2 m/s2, which she sustains for 0.9 s. Then, her acceler

ation drops to zero for the rest of the race. (a) What is her velocity at t = 0.9 s. m/s (b) What is her velocity at the end of the race? m/s
Physics
1 answer:
ad-work [718]3 years ago
6 0

Answer:

a) 3.78 m/s

b) 3.78 m/s

Explanation:

a )From the equations of kinematics   we know that

     Vf - Vi = at

since Initial speed Vi = 0

acceleration = 4.2 m/s2

so we have

     Vf = a t

           = (4.2) (0.9)

         = 3.78 m/s

velocity at t = 0.9 s. m/s is 3.78 m/s

b) If the sprinter maintains constant velocity then acceleration becomes zero.

   So velocity is 3.78 m/s

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During a 0.001 s interval while it is between the plates, the change of the momentum of the electron Δp with arrow is < 0, -8
Delvig [45]

Answer:

5.5 x 10^5 N/C

Explanation:

t = 0.001 s

Δp = - 8.8 x 10^-17 kg m /s

Force is equal to the rate of change of momentum.

F = Δp / Δt

F = (8.8 x 10^-17) / 0.001 = 8.8 x 10^-14 N

q = 1.6 x 10^-19 C

Electric field, E = F / q = (8.8 x 10^-14) / (1.6 x 10^-19)

E = 5.5 x 10^5 N/C

8 0
3 years ago
Assume your mass is 60 kg. The acceleration due to gravity is 9.8 m/s 2 . How much work against gravity do you do when you climb
Andre45 [30]

Answer:

W=1705.2 J

Explanation:

Given that

mass ,m= 60 kg

Acceleration due to gravity ,g= 9.8 m/s²

Height ,h= 2.9 m

As we know that work done by a force given as

W = F . d

F=force

d=Displacement

W=work done by force

Now by putting the values

F= m g (Acting downward  )

d= h  (Upward)

W= m g h    ( work done against the force)

W= 60 x 9.8 x 2.9 J

W=1705.2 J

Therefore the answer will be 1705.2 J.

8 0
3 years ago
What is the potential difference (voltage) if the resistance of 20 ohms produces a current of 10 amperes?
JulijaS [17]

Answer:

200 volts

Explanation:

Ohm's Law: V = IR

I = 10 A

R = 20 ohms

V = (10)(20) = 200 volts

8 0
2 years ago
In a laundromat, during the spin-dry cycle of a washer, the rotating tub goes from rest to its maximum angular speed of 2.2 rev/
Hunter-Best [27]

Answer:

n_{T} = 31.68\,rev

Explanation:

The angular acceleration is:

\ddot n_{1} = \frac{2.2\,\frac{rev}{s} -0\,\frac{rev}{s} }{8.8\,s}

\ddot n_{1} = 0.25\,\frac{rev}{s^{2}}

And the angular deceleration is:

\ddot n_{2} = \frac{0\,\frac{rev}{s}-2.2\,\frac{rev}{s} }{20\,s}

\ddot n_{2} = -0.11\,\frac{rev}{s^{2}}

The total number of revolutions is:

n_{T} = n_{1} + n_{2}

n_{T} = \frac{\left(2.2\,\frac{rev}{s} \right)^{2}-\left(0\,\frac{rev}{s} \right)^{2}}{2\cdot \left(0.25\,\frac{rev}{s^{2}} \right)} + \frac{\left(0\,\frac{rev}{s} \right)^{2}-\left(2.2\,\frac{rev}{s} \right)^{2}}{2\cdot \left(-0.11\,\frac{rev}{s^{2}} \right)}

n_{T} = 31.68\,rev

4 0
3 years ago
Tarzan has foolishly gotten himself into another scrape with the animals and must be rescued once again by Jane. The 60.0 kg Jan
Brut [27]

Complete part of Question: What is Jane's (and the vine's) angular speed just before she grabs Tarzan

Answer:

Jane's (and the vine's) angular speed just before she grabs Tarzan, w = 1.267 rad/s

Explanation:

According to the law of energy conservation:

Total change in kinetic energy = Total change in potential energy

Mass of Jane = 60 kg

Mass of the vine = 32 kg

Mass of Tarzan = 72 kg

Height of Tarzan = 5.50 m

Length of the vine = 8.50 m

Jane's change in gravitational potential energy,

U_J = 60 * 9.8 * 5.5\\U_J = 3234 J

Vine's gravitational potential energy,

U_v = Mgh/2\\U_v = 32*9.8*5.5/2\\U_v = 862.4J

Vine's Kinetic energy :

KE_V = 0.5 I w^{2} \\I_V = \frac{ML^2}{3} = \frac{32 * 8.5^2}{3} = 770.67 kg m^2\\ KE_V = 0.5 *770.67 * w^{2}\\KE_V = 385.33 w^{2}

Jane's Kinetic energy:

KE_J = 0.5m(wL)^2\\KE_J = 0.5*60(w * 8.5)^2\\KE_J = 2167.5 w^2

U_J + U_V = KE_J + KE_V

3234 + 862.4 = 2167.5w² + 385.33w²

4096.4 = 2552.83w²

w² = 4096.4/2552.83

w² = 1.605

w = √1.605

w = 1.267 rad/s

5 0
3 years ago
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