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3 years ago

A 2 kg ball is thrown upward with a velocity of 15 m/s. What is the kinetic energy of the ball as it is being thrown?

Physics

2 answers:

marusya05 [52]3 years ago

7 0

KE=1/2 m v^2
KE= .5 x 2kg x 15m/s to the 2nd power
KE=225 km/s

anyanavicka [17]3 years ago

5 0

Answer:

Kinetic energy = 225 J

Explanation:

As we know that kinetic energy is given as

$KE = \frac{1}{2}mv^2$

now here we know that

m = 2 kg

v = 15 m/s

now from above formula we know

$KE = \frac{1}{2}(2)(15)^2$

now we have

$KE = 225 J$

so kinetic energy of the moving ball is 225 J

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A tradesman sharpens a knife by pushing it with a constant force against the rim of a grindstone. The 30-cm-diameter stone is sp

Lorico [155]

Answer:

a. 0.21 rad/s2

b. 2.205 N

Explanation:

We convert from rpm to rad/s knowing that each revolution has 2π radians and each minute is 60 seconds

200 rpm = 200 * 2π / 60 = 21 rad/s

180 rpm = 180 * 2π / 60 = 18.85 rad/s

r = d/2 = 30cm / 2 = 15 cm = 0.15 m

a)So if the angular speed decreases steadily (at a constant rate) from 21 rad/s to 18.85 rad/s within 10s then the angular acceleration is

$\alpha = \frac{\Delta \omega}{\Delta t} = \frac{21 - 18.85}{10} = 0.21 rad/s^2$

b) Assume the grind stone is a solid disk, its moment of inertia is

$I = mR^2/2$

Where m = 28 kg is the disk mass and R = 0.15 m is the radius of the disk.

$I = 28*0.15^2/2 = 0.315 kgm^2$

So the friction torque is

$T_f = I\alpha = 0.315*0.21 = 0.06615 Nm$

The friction force is

$F_f = T_f/R = 0.06615 / 0.15 = 0.441 N$

Since the friction coefficient is 0.2, we can calculate the normal force that is used to press the knife against the stone

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2 years ago

A sled is pulled at a constant velocity across a horizontal snow surface. If a force of 100 N is being applied to the sled rope

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Answer:

60.18 N

Explanation:

Given that:

The force applied on the sled = 100 N

Suppose, the angle between the sled rope and the ground = 53°

The horizontal force which acts in the horizontal direction can be expressed as:

$F_x = F \ cos \theta$

$F_x = 100 \ cos (53)$

$F_x = 60.18 \ N$

But if the angle between the sled rope is parallel to the ground. Then, we use an angle on a straight line which is = 180°

$F_x = F \ cos \theta$

$F_x = 100 \ cos (180)$

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2 years ago

A current of 15.0 A flows through an electric heater operating on 120 V. Compute the power consumption of the electric heater.

Rzqust [24]

Answer:

There will be 1800 W power consumption in heater

Explanation:

We have given current flowing in the heater I = 15 A

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We know that power consumption is given by P = VI

So power consumption in heater = 120 × 15 = 1800 W

So there will be 1800 W power consumption in heater

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2 years ago

Army is standing still on the ground; Bill is riding his bicycle at 5 m/s eastward: and Carlos is driving his car at 15 m/s west

Aleks04 [339]

Explanation:

Given that,

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Taking eastward as positive direction, we have:

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Bill is moving 5 m/s eastward compared to Amy at rest, so the velocity of Bill's reference frame is

$v_B=+5\ m/s$

Therefore, Carlos velocity in Bill's reference frame will be

$v_c'=-15\ m/s-(+5\ m/s)\\\\=-20\ m/s$

So, the magnitude is 20 m/s and the direction is westward (negative sign).

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2 years ago