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larisa86 [58]
2 years ago
3

A ball travels with velocity given by [21] [ 2 1 ​ ], with wind blowing in the direction given by [3−4] [ 3 −4 ​ ] with respect

to some co-ordinate axes. What is the size of the velocity of the ball in the direction of the wind?
Physics
1 answer:
faust18 [17]2 years ago
3 0

Answer:

2/5 m/s

Explanation:

There are two vectors  v and w . Let θ be angle b/w the two vector.

cos\theta =\frac{\overleftarrow{v}\cdot \overleftarrow{w}}{\left | v \right |\left | w \right |}\\=\frac{6-4}{\sqrt(2^2+1^2)\sqrt(3^2+4^2)} =\frac{2}{5\sqrt(5)}

velocity of the ball in direction of the the wind

\left | vcos\theta \right |\\\left | v \right |cos\theta\\\sqrt(2^2+1^2)\frac{2}{5\sqrt(5)} = \frac{2}{5}

You might be interested in
A ball of mass m and radius R is both sliding and spinning on a horizontal surface so that its rotational kinetic energy equals
spin [16.1K]

Answer:

\frac{v_{cm}}{\omega} = 1.122\cdot R

Explanation:

According to the statement of the problems, the following identity exists:

K_{t} = K_{r}

\frac{1}{2}\cdot m \cdot v_{cm}^{2} = 0.63\cdot m \cdot R^{2} \cdot \omega^{2}

After some algebraic handling, the ratio is obtained:

\frac{v_{cm}^{2}}{\omega^{2}}=1.26\cdot R^{2}

\frac{v_{cm}}{\omega} = 1.122\cdot R

4 0
2 years ago
Which of the following are inertial reference frames? A. A car driving at steady speed on a straight and level road. B. A car dr
Aloiza [94]

Answers:

A. A car driving at steady speed on a straight and level road.

B. A car driving at steady speed up a 10∘ incline.

Explanation:

An object is said to be in an inertial reference frame if the net force acting on the object is zero. According to Newton's second law, this also means that the acceleration of the object is also zero:

F=ma

Since F=0, a=0 as well.

Let's now analyze each case.

A. A car driving at steady speed on a straight and level road. --> YES: this is an inertial reference frame, because the car is keeping a constant speed and a constant direction, so its velocity is not changing, and its acceleration is zero.

B. A car driving at steady speed up a 10∘ incline. --> YES: this is an inertial reference frame, because the car is keeping a constant speed and a constant direction, so its velocity is not changing, and its acceleration is zero.

C. A car speeding up after leaving a stop sign. --> NO: this is not an intertial reference frame, because the car is speeding up, so it is accelerating.

D. A car driving at steady speed around a curve. --> NO: this is not an inertial reference frame, because the car is changing direction, therefore its velocity is changing and so the car is accelerating.

So the only two choices which are correct are A and B.

8 0
2 years ago
Read 2 more answers
Do as physics instructor fred cauthen does and place a tennis ball close to and above the top of a basketball. drop the balls to
Ksivusya [100]

Answer:

after shock

creating a system for the conservation of the energy of the basketball ball and creating a system for the tennis ball only, the conservation of energy should be applied to each system independently

Explanation:

When the two balls fall they acquire the same speed since they are accelerated by the same force, their weight and the acceleration of the acceleration of gravity. When reaching the floor the mechanical energy of the system is conserved.

Upon reaching the floor, the first ball (basketball) collides with the floor, this process is very fast, at the end of the process the basketball comes out with a velicad up and collides with the much lighter tennis ball that is still descending .

we assume that the shocks are elastic, when solving the momentary and kinetic energy findings, we find the velocities after each shock

     

In this clash the tennis ball acquires a high kinetic speed with an upward direction that makes a very high height high. Again this shock is very fast and the tennis ball almost does not move.

Here we must separate the system, creating a system for the conservation of the energy of the basketball ball and another system for the tennis ball only, the conservation of energy should be applied to each system independently

Em₀ =K = 1/2 m v²

                    Em_{f} = U = m g h

As in the elastic shock the final speed of the tennis ball is approximately 2 vo, we can calculate the maximum height

                 m g h = 1/2 m (2v₀)²

                 h = 2 v₀²/g

To reconcile this with the conservation of energy we must calculate the energy for the tennis ball at two points, the first when the crash with the tennis ball ends and at the end point at its maximum height.

6 0
2 years ago
A student librarian lifts a 2.2 kg book from the floor to a height of 1.25 m. He carries the book 8.0 m to the stacks and places
Montano1993 [528]
The solution to your problem is as follows:


2.2Kg*9.8m/s = 21.56N 
<span>
21.56N*1.25m = 26.95J </span>


<span>We're only concerned with the work done against gravity, lifting the books to 1.25 meters. the distance walked has no effect on the problem, unless you take into account the wind resistance and the force needed to overcome it. Also, lowering the books onto the shelf doesnt count, because gravity does the work on the books.</span>
5 0
2 years ago
Read 2 more answers
Some gliders are launched from the ground by means of a winch, which rapidly reels in a towing cable attached to the glider. Wha
aliina [53]

Answer:

P=627.47W

Explanation:

To solve this problem we have to take into account, that the work done by the winch is

W=Fh

the force, at least must equal the gravitational force

F=Mg=(156kg)(9.8\frac{m}{s^2})=1258.8N

with force the tension in the cable makes the winch go up.

The work done is

W=(1258.8N)(58.0m)=73010.4J

To calculate the power we need to know what is the time t. But first we have to compute the acceleration

The acceleration will be

v_f^2=v_0+2ah\\a=\frac{v_f^2}{2h}=\frac{(24.9\frac{m}{s})}{2(58.0m)}=0.214\frac{m}{s^2}

and the time t

v_f=v_0+at\\t=\frac{v_f}{a}=116.35s

The power will be

P=\frac{W}{t}=\frac{73010.4J}{116.35s}=627.47W

HOPE THIS HELPS!!

6 0
2 years ago
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