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23 Nov 2019

You have to move a 300 kg box which is resting on a wooden floor(coefficient of friction = 0.5). There are 2 ways to get it tostart moving:

1) Push down on the box at an angle of 30 degrees from thehorizontal
2) Pull up on the box at an angle 30 degrees from thehorizontal

Which method should you choose, or are they equal? Provideexplanation.

I think that pushing down on the box makes much more sense b/c ifyou pull up at a 30 degree angle you are essentially having to liftthe box, which is much more difficult. I am looking for a morescientific answer.

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Bunny Greenfelder
Bunny GreenfelderLv2
9 Feb 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

Some Problems on Work
1. Joe is pulling a box of mass m = 10 kg up an inclined surface (?= 30degrees) using
a rope. The coefficient of kinetic friction between the surface andthe box is
µk = 0.5. It takes 10 seconds for Joe to bring up a box at aconstant velocity
V = 0.8m=s.
(a) What is the tension of the rope?
(b) What is the work done by the tension?
(c) What is the work done by the normal force?
(d) What is the work done by gravity?
(e) What is the total work done on the box?
(f) What is the power output necessary to Joe to bring up thebox?
maximal compression of the spring?
2. A block (m=50 kg) slides down a 3 m long inclined surface (? =30). The
coefficient of kinetic friction between the block and the surfaceis µk = 0.3.
Calculate the nal velocity of the block using the work-energytheorem.
3. A pendulum of length l and mass m is released from rest at anangle ? from
the equilibrium position.
(a) Neglect air friction. Calculate the velocity of the pendulumwhen the angle
is zero. Express your result in terms of ?, l, and m.
(b) Suppose ? = 60 degrees and l = 1 m. Suppose that the velocityof the pendulum
when the angle is zero is 1 m/s. Calculate the work done by the airfriction.
4. A point particle of mass m = 20 g is moving on a
at
surface when it reaches a slope which brigs it up by h = 08 m. Thespeed of
the particle in position A is v = 5 m/s.
(a) Suppose that there is no friction. What is the velocity of theparticle when
it reaches position B?
(b) Suppose that there is friction, and that the velocity of theparticle in B is
0. What is the work done by the friction from A to B?
5. A ball is shoot vertically with initial speed v, from a
table of height h.
(a) Calculate the maximal height ymax that the ball can reach (b)Calculate the velocity of the ball just before it hits thefloor.

In certain cities, parking spaces are at a premium and anyavailable surface will be used for parking, even highly slopedroofs. Consider the SUV parked in the picture above. If you are thedriver, how can you be sure that your car won’t flip overbackwards?
The schematic diagram below gives a simplified model of thesituation with the SUV on the slope. We are approximating the SUVas a uniform cube three meters long and two meters high, mounted ontires a half-meter in diameter that are set in a half meter fromthe edges of the vehicle. The SUV has a mass of 1500 kg. Forsimplicity, we will ignore the mass of the tires. Assume that thecoefficient of static friction between the tires and the road is0.8. Using the principles of static equilibrium, let’s determinewhether the car will stay on the slope. In order to maintain staticrotational equilibrium, the magnitudes of the normal forces on theforward and rear wheels must adjust to create a situation of zeronet torque. In order to maintain static translational equilibrium,the static friction forces between the tires and the road mustadjust to create a situation of zero net force. If the angle θ getstoo big, we will have a problem...
1. First, let’s assume that the angle θ is 30 degrees (note thewheels are locked and don’t roll) and the car is not moving. Whatis the magnitude of the normal force from the road on the frontwheels (top of incline)? On the back wheels (bottom of incline)?These normal force are unequal- why?
2. Now let’s take the situation to the extreme: what is the maximumvalue of the angle θ which is possible, if the SUV is to remain instatic equilibrium? First, determine the maximum angle that the carwon’t slide, and then determine the maximum angle that the carwon’t rotate. What happens to the SUV first if the angle isexceeded? What is the normal force on the front (top of incline)wheels in this situation?
3. Assume that it rains, and the coefficient of static friction isreduced from 0.8 to 0.5. Now what is the maximum value of the angleθ for which the car can remain in static equilibrium? If the angleθ exceeds this value, what happens to the SUV?

1. An object is dropped from a height.Once it is moving,which ofthe following statements are true,at least at one point?
a)its velocity is more than its accelerations
b)its velocity is less than its acceleration
c)its velocity is the same as its acceleration
d)its velocity is never equal to its acceleration

2. Which type of quantity is characterized by both magnitude anddirection?
a)scalar
b)vector
c)trigonometric
d)algebraic variable

3. A hiker walks 200m west and then walks 100m north. In whatdirection is her resulting displacement?
a)north
b)west
c)northwest
d)none of the answer is correct

4. Vector 1 is 7 units long and is at 70 degree. Vector 2 is 5units long and is at 225 degree. Vector 3 is a 3 units long and isat 150 degree. Which vector has equal magnitude components?
a)Vector 1
b)vector2
c)vector 3
d)none of the vectors has equal magnitude components??????

5. Which of the following is an example of the type of force thatacts at a distance?
a)gravitational
b)magnetic
c)electrical
d)all of the above

6. A crate weight W is being pushed across a horizontal surface bya force directed at an angle of 20 degrees below the horizontal.What is the magnitude of the normal force on the crate?
a)it is less then W
b)it equals W
c)it is more than W
d)none of the above since the coefficient of kinetic friction isnot given

7. The net force on an object is in the positive x-direction.Consider the following statements.
(i) The object can be moving in the negative x-direction.
(ii) The object can be speeding up.
(iii) The object can be slowing down.
(iv) The object can be moving in the positive y-direction.

Which of the statements are true?
a. (i) and (ii)
b. (ii) and (iii)
c. (iii) and (iv)
d. Choose this answer if all the statements are true.

8.The work done by static friction can be:
a. positive.
b. negative.
c. zero.
d. Any of the above.

9.The rate at which work is done is equivalent to which of thefollowing?
a. increase in potential energy
b. thermal energy
c. potential energy
d. power

10.The dimensional equivalent of the quantity impulse in terms ofthe fundamental quantities (mass, length,
time) is which of the following?
a. MLT-1
b. ML2T-2
c. MLT
d. MLT-2

11. The dimensional equivalence of the quantity "momentum" in termsof the fundamental quantities (mass,
length, time) is:
a. MLT-1.
b. ML2T-2.
c. MLT.
d. MLT-2.

12.In order for a satellite to be geosynchronous, its orbitmust:
a. go over the North and South Poles.
b. be over the equator.
c. be over a single longitude.
d. emit television signals.

13. The quantity "angular momentum" (in terms of the fundamentalquantities of mass, length, and time) is equivalent
to:
a. MLT-2.
b. ML2T-1.
c. ML2T-3.
d. ML3T.
d. MLT-2.

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