# various problems in classical physics

When a mass of 25.0 grams is suspended from a certain spring and lowered slowly until the spring stops stretching, the spring stretches 2.00 cm. What is the spring constant of the spring?

a. 1.25 N/m

b. 0.800 N/m

c. 7.85 N/m

d. 12.3 N/m

A mass of 40.0 grams is attached to a vertical spring with a spring constant k = 20.0 N/m and lowered slowly until the spring stops stretching. How much does the spring stretch?

a. 0.00200 m

b. 0.0196 m

c. 0.0816 m

d. 0.800 m

A tightrope walker with a mass of 60.0 kg stands at the center of a rope which was initially strung horizontally between two poles. His weight causes the rope to sag symmetrically, making an angle of 4.80degree with the horizontal. What is the tension in the rope?

a. 359 N

b. 589 N

c. 2470 N

d. 3520 N

A tightrope walker with a mass of 60.0 kg stands at the center of a rope which was initially strung horizontally between two poles 50.0 m apart. His weight causes the rope to sag 1.20 m. What is the tension in the rope?

a. 589 N

b. 1250 N

c. 6130 N

d. 25400 N

A 2-kg ball is moving with a constant speed of 5 m/s in a horizontal circle whose radius is 50 cm. What is the acceleration of the ball?

a. 0 m/s squared.

b. 10 m/s squared.

c. 20 m/s squared.

d. 50 m/s squared.

A 2-kg ball is moving with a constant speed of 5 m/s in a horizontal circle whose radius is 50 cm. What is the magnitude of the net force on the ball?

a. 0 N

b. 20 N

c. 40 N

d. 100 N

When an object moves at constant speed on a circular path, which of the following is true?

a. A net force pointing along the direction of motion acts on the object.

b. A net force pointing away from the center of the circle acts on the object.

c. The net force acting on the object is zero N.

d. A net force pointing towards the center of the circle acts on the object.

The SI unit of work is expressed as:

a. Watt.

b. Newton.

c. Newton/second.

d. Joule.

The work done by the centripetal force on an object with a mass of 1 kg moving with a constant velocity of 4 m/s into a circular path of radius 0.6 m for one full cycle is:

a. 100.7 J

b. 3.8 J

c. 0 J

d. 80 J

How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

a. 1.10 MJ

b. 10.0 kJ

c. 40.0 kJ

d. 0.960 MJ

An object of mass 10.0 kg is initially at rest. A 100 N force causes it to move horizontally through a distance of 6.00 m. What is the change in the kinetic energy of this object?

a. 0 J

b. 200 J

c. 60.0 J

d. 600 J

A weight of 200 N is hung from a spring with a spring constant of 2500 N/m and lowered slowly. How much will the spring stretch?

a. 4.00 cm

b. 6.00 cm

c. 8.00 cm

d. 10.0 cm

In the SI system of units, power has the same units as:

a. Js/m.

b. Jm/s.

c. Nm/s.

d. W/m.

The ratio of power outputs of Jack and Jill is 2:1 to complete a certain amount of work. If Jill takes 4 minutes to complete this work, how long will Jack take to finish the same work?

a. 2 minutes.

b. 8 minutes.

c. 6 minutes.

d. 4 minutes.

As compared to Jack, Jill does twice the work in half the time. Jill's power output is

a. The same as Jack's power output.

b. One-half as much as Jack's power output.

c. Twice Jack's power output.

d. Four times Jack's power output.

An ordinary light bulb consumes 40 W of power. Through what height could a 1000-N object be lifted expending the same amount of power for 6 hours?

a. 860 m

b. 360 m

c. 720 m

d. 650 m

An object of mass 20 kg is raised vertically through a distance of 8.0 m above ground level. Using g = 10 m/s squared what is the potential energy of this object at this position?

a. 160 N/m

b. 160 Nm

c. 1600 N/m

d. 1600 Nm

A mass of 1.0 kg is pushed against a spring with a spring constant of 25 N/m. As a result, the spring is compressed by 20 cm. The mass is then released. What is the amount of potential energy acquired by the spring when it is compressed?

a. 5.0 J

b. 0.20 J

c. 0.50 J

d. 10 J

The ratio of the potential energy to the kinetic energy of an object of mass m at a height of 40 m above ground level is 2:1. What is the speed of the object at that point? Use g = 10 m/s squared:

a. 10 m/s

b. 20 m/s

c. 30 m/s

d. 40 m/s

What should the height of a slide in a park be so that a child will reach the bottom of the slide with a speed of 15.0 m/s? Use g = 10.0 m/s squared:

a. 22.5 m

b. 15.1 m

c. 11.3 m

d. 10.5 m

A snowboarder coasts on a smooth track that rises from one level to another. If the snowboarder's initial speed is 4 m/s, the snowboarder just makes it to the upper level and comes to rest. With a slightly greater initial speed of 5 m/s, the snowboarder is still moving to the right on the upper level. What is the snowboarder's final speed in this case?

a. 1 m/s

b. 2 m/s

c. 3 m/s

d. 4 m/s

A firecracker breaks up into two pieces, one has a mass of 200 g and flies off along the x-axis with a speed of 82.0 m/s and the second has a mass of 300 g and flies off along the y-axis with a speed of 45.0 m/s. What is the total momentum of the two pieces?

a. 361 kg x m/s at 56.3 degrees from the x-axis.

b. 93.5 kg x m/s at 28.8 degrees from the x-axis.

c. 21.2 kg x m/s at 39.5 degrees from the x-axis.

d. 361 kg x m/s at 0.983 degrees from the x-axis.

Two air track carts move along an air track towards each other. Cart A has a mass of 450 g and moves toward the right with a speed of 0.850 m/s and air track cart B has a mass of 300 g and moves toward the left with a speed of 1.12 m/s. What is the total momentum of the system?

a. 0.047 kg x m/s toward the right.

b. 0.719 kg x m/s toward the right.

c. 0.750 kg x m/s toward the right.

d. 0.750 kg m/s toward the left.

A golf club exerts an average force of 1000 N on a 0.045-kg golf ball which is initially at rest. The club is in contact with the ball for 1.8 ms. What is the speed of the golf ball as it leaves the tee?

a. 35 m/s

b. 40 m/s

c. 45 m/s

d. 50 m/s

A 0.330-kg volleyball is thrown vertically downward with a speed of 0.150 m/s. It takes it 0.0655 s to reach the ground. What is the magnitude of its momentum just before it hits the ground?

a. 0.212 kg x m/s

b. 0.262 kg x m/s

c. 0.163 kg m/s

d. 0.0216 kg x m/s

In a collision between two unequal masses, how does the impulse imparted to the smaller mass by the larger mass compare with the impulse imparted to the larger mass by the smaller one?

a. It is larger.

b. It is smaller.

c. They are equal.

d. The answer depends on how fast they are moving.

A batter hits a 0.140-kg baseball that was approaching him at 40.0 m/s and, as a result, the ball leaves the bat at 30.0 m/s in the direction of the pitcher. What is the magnitude of the impulse delivered to the baseball?

a. 9.80 Ns

b. 1.40 Ns

c. 5.60 Ns

d. 7.00 Ns

A 60.0-kg man stands at one end of a 20.0-kg uniform 10.0-m long board. How far from the man is the center of mass of the man-board system?

a. 1.25 m

b. 2.50 m

c. 5.00 m

d. 7.50 m

A triangle has angles of 1.02 radians and 0.85 radians. What is the third angle?

a. 1.27 rad

b. 1.13 rad

c. 2.13 rad

d. 4.41 rad

An object is moving in a circular path with an angular speed of 1.52 rad/s. How long does it take the object to complete one revolution?

a. 4.13 s

b. 2.07 s

c. 118 s

d. 4.77 s

A wheel that is rotating at 33.3 rad/s is given an angular acceleration of 2.15 rad/s to power of (exponent). Through what angle has the wheel turned when its angular speed reaches 72.0 rad/s?

a. 83.2 rad

b. 697 rad

c. 66.8 rad

d. 948 rad

When a car is weighed, it is allowed to move over a scale which records a reading as the front wheels go over the scale, and a second reading when the rear wheels go over the scale. The weight of the car is equal to:

a. The weight under the front wheels.

b. The weight under the rear wheels.

c. The average of the two weights.

d. The sum of the two weights.

A 320-g mass and a 400-g mass are attached to the two ends of a string that goes over a pulley with a radius of 8.70 cm. Because of friction, the pulley does not begin to rotate. What is the magnitude of the frictional torque on the bearing of the pulley if the system is in static equilibrium?

a. 0.00683 Nm

b. 0.614 Nm

c. 0.0626 Nm

d. 0.000696 Nm

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#### Solution Summary

The solution is comprised of detailed explanations of various problems in classical physics, such as spring, circular motion, conservation of energy, conservation of momentum, etc.

Physics - Classical Mechanics Problem

Please help with the following problem.

A 2.50 kg object placed on a frictionless, horizontal table is connected to a string that passes over a pulley and then is fastened to a hanging 7.50 kg object, as shown in the figure. Find the magnitude of the acceleration of the two objects and the tension in the string. Show all work. (Please see the attached file for full problem description)

acceleration of the 2.50 kg object =

acceleration of the 7.50 kg object =

tension in string =

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