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3 years ago

When an object rolls over a surface, the kind of friction that occurs is called

Physics

1 answer:

maks197457 [2]3 years ago

6 0

Answer:

False, When an object rolls over a surface, the kind of friction that occurs is called ROLLING FRICTION

Explanation:

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A ball has a mass of 1.5kg and is thrown straight up with a speed of 60m/s, what is the ball’s momentum:

madam [21]

Answer:

Assumption: the air resistance on this ball is negligible. Take $g = 10\; \rm m \cdot s^{-2}$ .

a. The momentum of the ball would be approximately $60\;\rm kg \cdot m \cdot s^{-1}$ two seconds after it is tossed into the air.

b. The momentum of the ball would be approximately $\rm \left(-45\; \rm kg \cdot m \cdot s^{-1}\right)$ three seconds after it reaches the highest point (assuming that it didn't hit the ground.) This momentum is smaller than zero because it points downwards.

Explanation:

The momentum $p$ of an object is equal its mass $m$ times its velocity $v$ . That is: $\vec{p} = m \cdot \vec{v}$ .

Assume that the air resistance on this ball is negligible. If that's the case, then the ball would accelerate downwards towards the ground at a constant $g \approx -10\; \rm m \cdot s^{-2}$ . In other words, its velocity would become approximately $10\; \rm m \cdot s^{-1}$ more negative every second.

The initial velocity of the ball is $60\; \rm m \cdot s^{-1}$ . After two seconds, its velocity would have become $60\;\rm m \cdot s^{-1} + 2\; \rm s \times \left(-10\;\rm m \cdot s^{-1}\right) = 40\; \rm m \cdot s^{-1}$ . The momentum of the ball at that time would be around $p = m \cdot v \approx 60\; \rm kg \cdot m \cdot s^{-1}$ .

When the ball is at the highest point of its trajectory, the velocity of the ball would be zero. However, the ball would continue to accelerate downwards towards the ground at a constant $g \approx -10\; \rm m \cdot s^{-2}$ . That's how the ball's velocity becomes negative.

After three more seconds, the velocity of the ball would be $0\; \rm m \cdot s^{-1} + 3\; \rm s \times \left(-10\; \rm m \cdot s^{-2}\right) = -30 \; \rm m \cdot s^{-1}$ . Accordingly, the ball's momentum at that moment would be $p = m \cdot v \approx \left(-45\; \rm kg \cdot m \cdot s^{-1}\right)$ .

3 0

3 years ago

Can a particle with constant speed be accelarating? what if it has constant velocity?

Olin [163]

Explanation:

it can be safely concluded that an object moving in a circle at constant speed is indeed accelerating. It is accelerating because the direction of the velocity vector is changing.

When an object is moving with constant velocity, it does not change direction nor speed and therefore is represented as a straight line when graphed as distance over time.

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3 years ago

Does sand stay sand forever?

Gemiola [76]

Answer:

No sand doesn't stay sand forever.

Explanation:

We may have a thought that the sand we see on the beach areas are always the same one for eternal, but it is not true.
Due to different activities like beach nourishment, sand replenishment etc. the sand in the beach areas are changed and replaced.
If the sand remained there for long time, it also affects the sand eating organisms and plants.

3 0

3 years ago

A train travels 57 kilometers in 3 hours, and then 87 kilometers in 2 hours. What is its average speed? km/hr

skad [1K]

Average speed (v) = total distance(d) / total time (t)
d = 57 + 87km = 144km
t = 2 + 3hrs = 5hrs
v = d÷t = 144÷5 = 28.8km/hr

3 0

2 years ago

What color is seen when the red light is on

Dennis_Churaev [7]

Answer:

Red is seen

Explanation:

8 0

2 years ago