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jeka57 [31]
3 years ago
12

A box is being pushed across the floor at a constant velocity with an

Physics
1 answer:
Oksana_A [137]3 years ago
8 0

Answer:

<em>Magnitude of frictional force = 30 N</em>

Explanation:

According to the second Newton's law, the net force exerted by an external agent on an object of mass m is:

Fn=m.a

The net force is the vector addition of each individual force. If the sum of all the forces acting on an object is zero, then the acceleration is zero. That means the object moves at a constant speed or is at rest.

When an object is pushed across a horizontal rough surface, there are two forces acting in the direction of the motion: The applied force and the frictional force.

If the applied force is greater than the frictional force, then the object moves at a constant positive acceleration. If the frictional force is greater than the applied force, then the object won't move at all (if it was at rest) or will start a deaccelerated motion (braking).

Finally, if both forces are equal, the object will move at a constant speed or remains at rest. Since the box is moving at a constant speed, we can conclude the frictional force equals the applied force:

Magnitude of frictional force = 30 N

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In Example 2.12, two circus performers rehearse a trick in which a ball and a dart collide. Horatio stands on a platform 6.4 m a
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Answer:

time of collision is

t = 0.395 s

h = 5.63 m

so they will collide at height of 5.63 m from ground

Explanation:

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similarly initial speed of the object which is projected by spring is given as

v_2 = 16.2 m/s

now relative velocity of object with respect to ball

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now since we know that both are moving under gravity so their relative acceleration is ZERO and the relative distance between them is 6.4 m

d = v_r t

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Now the height attained by the object in the same time is given as

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h = 16.2(0.395) - \frac{1}{2}(9.81).395^2

h = 5.63 m

so they will collide at height of 5.63 m from ground

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From tables, the speed of sound at 0°C is approximately
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