Which of the following describes a reference point?

1 answer:

3 0

The best answer is A.

Imagine you are looking out a car window and you see a tree. A few seconds later you do not see the tree where it was. You have used the tree as a reference point to know that the car is moving.

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A 10 kg runaway grocery cart runs into a spring with spring constant 250 n/m and compresses it by 60 cm. what was the speed of t

andrew-mc [135]

The initial kinetic energy of the cart is
$K= \frac{1}{2} mv^2$ (1)
where m is the mass of the cart and v its initial velocity.

Then, the cart hits the spring compressing it. The maximum compression occurs when the cart stops, and at that point the kinetic energy of the cart is zero, so all its initial kinetic energy has been converted into elastic potential energy of the spring:
$U= \frac{1}{2}kx^2$
where k is the spring constant and x is the spring compression.

For energy conservation, K=U. We can calculate U first: the compression of the spring is x=60 cm=0.60 m, while the spring constant is k=250 N/m, so
$U= \frac{1}{2}kx^2= \frac{1}{2}(250 N/m)(0.60 m)^2=45 J$

So, the initial kinetic energy of the cart is also 45 J, and from (1) we can find the value of the initial velocity:
$v= \sqrt{ \frac{2K}{m} }= \sqrt{ \frac{2 \cdot 45 J}{10 kg} } =3 m/s$

7 0

3 years ago

A pilot is flying from DFW to NYC. The air traffic controller directs him to fly 69° Northeast at 243 m/s. What is the y compone

kolezko [41]

Answer:

$v_{y} = 227$ m/s

Explanation:

Assumptions: 0° is true North, and 90° is east (along the x-axis).

To solve this problem we must use the expression:

$v_{y} = v_{0}sin(\theta)$

Where $v_{y}$ is the velocity in the y-direction (East), $v_{0}$ is the total velocity in the direction which the aircraft is travelling, and $\theta$ is the direction the aircraft is travelling (angle from the y-axis).