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3 years ago

Quick Physics Review Questions!!

1 answer:

6 0

I think the correct answer from the choices listed above is the last option. It is only specific heat accounts for mass not heat capacity. Specific heat is specific for a certain amount and has units of <span> J/ kg-K. As you can see, the denominator has kg which is a unit of mass.</span>

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In an old-fashioned amusement park ride, passengers stand inside a 4.9-m-diameter hollow steel cylinder with their backs against

Viefleur [7K]

Answer:

24.07415 rpm

Explanation:

$\mu$ = Coefficient of friction = 0.63

v = Velocity

d = Diameter = 4.9 m

r = Radius = $\frac{d}{2}=\frac{4.9}{2}=2.45\ m$

m = Mass

g = Acceleration due to gravity = 9.81 m/s²

Here the frictional force balances the rider's weight

$f=\mu F_n$

The centripetal force balances the weight of the person

$\mu m\frac{v^2}{r}=mg\\\Rightarrow \mu \frac{v^2}{r}=g\\\Rightarrow v=\sqrt{\frac{gr}{\mu}}\\\Rightarrow v=\sqrt{\frac{9.81\times 2.45}{0.63}}\\\Rightarrow v=6.17656\ m/s$

Velocity is given by

$v=\omega r\\\Rightarrow \omega=\frac{v}{r}\\\Rightarrow \omega=\frac{6.17656}{2.45}\\\Rightarrow \omega=2.52104\ rad/s$

Converting to rpm

$2.52104\times \frac{60}{2\pi}=24.07415\ rpm$

The minimum angular speed for which the ride is safe is 24.07415 rpm

4 0

2 years ago

A 3.06kg stone is dropped from a height of 10.0m and strikes the ground with a velocity of 7.00m/s. What average force of air fr

xxTIMURxx [149]

<span>22.5 newtons. First, let's determine how much energy the stone had at the moment of impact. Kinetic energy is expressed as: E = 0.5mv^2 where E = Energy m = mass v = velocity Substituting known values and solving gives: E = 0.5 3.06 kg (7 m/s)^2 E = 1.53 kg 49 m^2/s^2 E = 74.97 kg*m^2/s^2 Now ignoring air resistance, how much energy should the rock have had? We have a 3.06 kg moving over a distance of 10.0 m under a force of 9.8 m/s^2. So 3.06 kg * 10.0 m * 9.8 m/s^2 = 299.88 kg*m^2/s^2 So without air friction, we would have had 299.88 Joules of energy, but due to air friction we only have 74.97 Joules. The loss of energy is 299.88 J - 74.97 J = 224.91 J So we can claim that 224.91 Joules of work was performed over a distance of 10 meters. So let's do the division. 224.91 J / 10 m = 224.91 kg*m^2/s^2 / 10 m = 22.491 kg*m/s^2 = 22.491 N Rounding to 3 significant figures gives an average force of 22.5 newtons.</span>

3 0

3 years ago

In a certain time period a coil of wire is rotated from one orientation to another with respect to a uniform 0.38-T magnetic fie

juin [17]

<h2>The emf produced is 7.2 V</h2>

Explanation:

When coil is placed in the magnetic field , the flux attached with it can be found by the relation . Flux Ф = the dot product of magnetic field and area of coil .

Thus Ф = B A cosθ

here B is magnetic field strength and A is the area of coil .

The angle θ is the angle between coil and field direction .

When coil rotates , the angle varies . By which the flux varies . The emf is produced in coil due to variation of flux . The relation for this is

The emf produced ξ = - $\frac{d\phi}{dt}$ = B A sinθ $\frac{d\theta}{dt}$

Now in the given problem

5 = 0.38 x A x $\frac{d\theta}{dt}$ I

Now if the magnetic field is 0.55 T and all the other terms are same , the emf produced

ξ = 0.55 x A x $\frac{d\theta}{dt}$ Ii

dividing II by I , we have

$\frac{\xi}{5}$ = $\frac{0.55}{0.38}$ = 1.45

or ξ = 7.2 V

6 0

3 years ago

A mover pushes a 30 kg crate across a level florr with a force of 250 N, but the crate accelerates at a rate of only 5.83 m/s sq

arlik [135]

Force of friction=75 N

Explanation:

we use Newton's second law of motion

F- Ff= ma

F = applied force=250 N

Ff= force of friction

a= acceleration= 5.83 m/s²

m= mass=30 kg

250- Ff= 30 (5.83)

Ff=250-30(5.83)

Ff=250-175

Ff=75 N

7 0

3 years ago

A small fish is dropped by a pelican that is rising steadily at 0.500 m/s. How far below the pelican is the fish after 2.50 s?

sesenic [268]

Refer to the diagram shown below.

h = original height of the pelican when the fish is dropped (not relevant).
S = distance traveled by the fish as a function of time, measured upward.
u = 0.5 m/s, the upward velocity with which the fish is dropped.
g = 9.8 m/s², the acceleration due to gravity.

Use the following equation:
S = ut + (1/2)gt²

S = (0.5 m/s)*(2.5 s) + 0.5*(-9.8 m/s²)*(2.5 s)²
= -29.375 m

The negative sign means that the fish drops by 29.375 m from the original height of h.

Answer: The fish is 29.375 m below where the pelican dropped it after 2.5 s.

7 0

3 years ago