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3 years ago

A ball rolls forward in the grass slowing down as it rolls?

Physics

1 answer:

olga nikolaevna [1]3 years ago

3 0

Yes it does, uh huh. It slows down as it rolls. That's a fact.

In order for the ball to roll forward, it has to push grass out of the way. That takes energy. To bend each blade of grass out of its way, the ball has to use a tiny bit of the kinetic energy that it has, so it gradually runs out of kinetic energy. When its kinetic energy is all gone, it stops moving.

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A box is pushed horizontally with constant speed across a rough horizontal surface. Which of the following must be true?

Pavel [41]

D

Because if an object is moving at a constant speed the force of friction must equal the applied (horizontal) force, and for it to be accelerating or decelerating, the force of friction and the applied force must be unequal

5 0

2 years ago

A car travels a distance of 100 km. For the first 30 minutes it is driven at a constant speed of 80 km/hr. The motor begins to v

gregori [183]

Explanation:

First, we need to determine the distance traveled by the car in the first 30 minutes, $d_{\frac{1}{2}}$ .

Notice that the unit measurement for speed, in this case, is km/hr. Thus, a unit conversion of from minutes into hours is required before proceeding with the calculation, as shown below

$d_{\frac{1}{2}\text{h}} \ = \ \text{speed} \ \times \ \text{time taken} \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 80 \ \text{km h}^{-1} \ \times \ \left(\displaystyle\frac{30}{60} \ \text{h}\right) \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 80 \ \text{km h}^{-1} \ \times \ 0.5 \ \text{h} \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 40 \ \text{km}$

Now, it is known that the car traveled 40 km for the first 30 minutes. Hence, the remaining distance, $d_{\text{remain}}$ , in which the driver reduces the speed to 40km/hr is

$d_{\text{remain}} \ = \ 100 \ \text{km} \ - \ 40 \ \text{km} \\ \\ \\ d_{\text{remain}} \ = \ 60 \ \text{km}$ .

Subsequently, we would also like to know the time taken for the car to reach its destination, denoted by $t_{\text{remian}}$ .

$t_{\text{remain}} \ = \ \displaystyle\frac{\text{distance}}{\text{speed}} \\ \\ \\ t_{\text{remain}} \ = \ \displaystyle\frac{60 \ \text{km}}{40 \ \text{km hr}^{-1}} \\ \\ \\ t_{\text{remain}} \ = \ 1.5 \ \text{hours}$ .

Finally, with all the required values at hand, the average speed of the car for the entire trip is calculated as the ratio of the change in distance over the change in time.

$\text{speed} \ = \ \displaystyle\frac{\Delta d}{\Delta t} \\ \\ \\ \text{speed} \ = \ \displaystyle\frac{100 \ \text{km}}{(0.5 \ \text{hr} \ + \ 1.5 \ \text{hr})} \\ \\ \\ \text{speed} \ = \ \displaystyle\frac{100 \ \text{km}}{2 \ \text{hr}} \\ \\ \\ \text{speed} \ = \ 50 \ \text{km hr}^{-1}$

Therefore, the average speed of the car is 50 km/hr.

8 0

2 years ago

A star’s parallax angle is 1.0. How far away is the star in light years?

larisa [96]

Distance = 2AU / tan1.0

If you mean 1.0 is in degrees, then Distance = 114.58 AU

7 0

2 years ago

Read 2 more answers

Ana wonders how light can affect a mystery material. The table below shows what happens when different types of light hit the my

vivado [14]

The light can definitely change the mystery material. This can occur through a change in temperature or color (option C).

A material is affected by light mainly if the material absorbs the light. Based on the chart, we know this mystery material can absorb two types of light:

Red light.
Yellow light.

Moreover, this phenomenon can lead to two main changes:

Change in temperature: Light affects materials by increasing their temperature of these. A common example is the way the temperature of an object increases if it is exposed to sunlight.
Change in color: Some materials react to light by changing their color.

Based on this, the material can change its color or temperature.

Note: This question is incomplete; here is the missing part:

A. Yes, but the mystery material can change in only one way, such as by getting warm, because all the light that a material absorbs will affect that material in the same way.

B. No. The mystery material can’t change because the light is not a physical thing. Light cannot change physical things like the mystery material.

C. Yes and the mystery material can change in one or two different ways, such as by getting warm and/or changing color, because different types of light can cause different changes to a material when they are absorbed.

D. There is no way to know whether the mystery material will change or not.

Learn more about sunlight in: brainly.com/question/1603783

3 0

2 years ago

You push your friend, whose mass is 54kg, down a hill so she can go sledding. Her acceleration is 3m/s2. Calculate the amount of

Alecsey [184]

Answer:

18 newtons

Explanation:

Divide weight by speed

3 0

2 years ago