the average velocity of a bus is 15 m/s. If it starts off going 15m north and then 20m south, how long will the bus ride take?

A plastic film moves over two drums. During a 4-s interval the speed of the tape is increased uniformly from v0 = 2ft/s to v1 =

Ratling [72]

Answer:

Question 1)

a) The speed of the drums is increased from 2 ft/s to 4 ft/s in 4 s. From the below kinematic equations the acceleration of the drums can be determined.

$v_1 = v_0 + at \\4 = 2 + 4a\\a = 0.5~ft/s^2$

This is the linear acceleration of the drums. Since the tape does not slip on the drums, by the rule of rolling without slipping,

$v = \omega R\\a = \alpha R$

where α is the angular acceleration.

In order to continue this question, the radius of the drums should be given.

Let us denote the radius of the drums as R, the angular acceleration of drum B is

α = 0.5/R.

b) The distance travelled by the drums can be found by the following kinematics formula:

$v_1^2 = v_0^2 + 2ax\\4^2 = 2^2 + 2(0.5)x\\x = 12 ft$

One revolution is equal to the circumference of the drum. So, total number of revolutions is

$x / (2\pi R) = 6/(\pi R)$

Question 2)

a) In a rocket propulsion question, the acceleration of the rocket can be found by the following formula:

$a = \frac{dv}{dt} = -\frac{v_{fuel}}{m}\frac{dm}{dt} = -\frac{13000}{2600}25 = 125~ft/s^2$

b) $a = -\frac{v_{fuel}}{m}\frac{dm}{dt} = - \frac{13000}{400}25 = 812.5~ft/s^2$

5 0

4 years ago

a bat experts a 120 N force on a 0.134 kg baseball for 0.04 seconds. what impolse is excerted on the bat

musickatia [10]

The impulse exerted by a force F on an object in a time $\Delta t$ is given by
$I = F \Delta t$
In our problem, we have a force of 120 N: F=120 N, applied to the baseball for a time of $\Delta t=0.04 s$ . Therefore the impulse is
$I=F \Delta t = (120 N)(0.04 s)=4.8 Ns$

3 0

4 years ago

What's three pieces of evidence that Wegener used to support his theory ( Alfred Wegener’s hypothesis of continental drift state

Elis [28]

Answer:

In the early part of the 20th century, scientists began to put together evidence that the continents could move around on Earth's surface. The evidence for continental drift included the fit of the continents; the distribution of ancient fossils, rocks, and mountain ranges; and the locations of ancient climatic zones.

6 0

3 years ago

A beach ball with a volume of 5,000 cm3 is pushed underwater. What is the magnitude of the buoyant force pushing upwards? The de

Kobotan [32]

<h2>Hello!</h2>

The answer is:

The buoyant force is equal to 49N.

The buoyant force is the force that pushes upwards and object when it's submerged in water, this force is always trying to move the object to the surface of the liquid or water. We must consider that the volume of water or liquid displaced is equal to the volume of the submerged object.

We can calculate the buoyant force using the following formula:

$F_{B}=Density*VolumeDisplaced*GravityAcceleration$