PHY 2048 Lecture Notes - Lecture 4: Net Force, Friction, Centripetal Force

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ceruleancrocodile714

14 Jun 2021

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Anyobject continues in its state of rest or uniform motion in straight line until acted upon by a net force tf ef 0 97 0. If object a applies a force on object b b also applies same force on a but in the opposite direction. M 2 dimension x eifx max y sfy may. A force on the object perpendicularto the surface of contact appliedby the surface n. Friction actsalongthe surface of contact and opposes the motion of theobject f. For the forces not acting either along x or y direction find the x and y components of those forces. Use newton"s 2nd law accordingly a if mass of the object is 3 kg and. 4 n y n"t n find the acceleration of object when f friction. F not acting on x or y 50 find components. F f becauseobjecthas no acceleration in the y direction. Fsino n w tf n w fsimonmg fsino.

Related Questions

1) An object is moving with constant velocity. Which of thefollowing statements is true?
a) A constant force is being applied in the direction ofmotion.
b) A constant force is being applied in the direction opposite ofmotion.
c) There are no forces acting on the object.
d) The net force on the object is zero.
e) There is no frictional force acting on the object.

2) You apply the same force to two objects. Object 1 has mass M andobject 2 has mass 5M.
a) ten times that of object 1 b) five times that of object 1
c) the same as that of object 1 d) 1/5 as that of object 1

3) An object of weight W is in free-fall close to the surface ofEarth. What is the force that the object exerts on Earth?
a) a force greater than W b) a force less than W
c) a force equal to W d) no force at all

4) A parking crate slides down an inclined ramp at constantvelocity. Thus we can deduce that _
a) a frictional force is acting on it
b) a net downward force is acting on it
c) a net upward force is acting on it
d) it is not acted on by appreciable normal force
e) it is not acted on by appreciable gravitational force

5) A person applies a constant force of 20N to a rock of mass1000kg for a total of 20 seconds. What is the work done by thisperson if the person does not move at all by this appliedforce?
a) 1000J b) 2000J c) 20,000J d) 0J e) 400J

6) If the net work done on an object is positive, then theobject's kinetic energy.
a) decreases b) remains the same c) increases d) is zero

7) You throw a ball straight up. Compare the sign of the workdone by gravity while the ball goes up with the sign of the workdone by gravity while it goes down.
a) Work is + on the way up and + on the way down
b) Work is + on the way up and - on the way down
c) Work is - on the way up and + on the way down
d) Work is - on the way up and - on the way down

1) An object is moving with constant velocity. Which of the following statements is true?
a) A constant force is being applied in the direction of motion.
b) A constant force is being applied in the direction opposite of motion.
c) There are no forces acting on the object.
d) The net force on the object is zero.
e) There is no frictional force acting on the object.

2) You apply the same force to two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration is
a) ten times that of object 1 b) five times that of object 1
c) the same as that of object 1 d) 1/5 as that of object 1

3) An object of weight W is in free-fall close to the surface of Earth. What is the force that the object exerts on Earth?
a) a force greater than W b) a force less than W
c) a force equal to W d) no force at all

4) A parking crate slides down an inclined ramp at constant velocity. Thus we can deduce that _
a) a frictional force is acting on it
b) a net downward force is acting on it
c) a net upward force is acting on it
d) it is not acted on by appreciable normal force
e) it is not acted on by appreciable gravitational force

5) A person applies a constant force of 20N to a rock of mass 1000kg for a total of 20 seconds. What is the work done by this person if the person does not move at all by this applied force?
a) 1000J b) 2000J c) 20,000J d) 0J e) 400J

6) If the net work done on an object is positive, then the object's kinetic energy.
a) decreases b) remains the same c) increases d) is zero

7) You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
a) Work is + on the way up and + on the way down
b) Work is + on the way up and - on the way down
c) Work is - on the way up and + on the way down
d) Work is - on the way up and - on the way down

lavenderbat941

A particle of mass m is constrained to move on the inside surfaceof a cone of half-angle a, under the influence of constantgravitational force. In the cylindrical coordinates (r, phi, z) theconstraint that the particle is moving on the surface of the coneis given by z=r cot a . [do not use lagrangian mothod)

a) Find the net force acting on the particle and derive theequation of motion for r and phi using Newton's 2nd law. Show thatthe angular momentum L is a constant of motion. (use a incylindrical coordinateshttp://mathworld.wolfram.com/CylindricalCoordinates.html
see eq 72)
b) Find the total energy in terms of r, r dot and L

My attempt:

a) I found all the forces acting on the particle and set them equalto the forces I get from using the acceleration in cylindricalcoordinates

so, F(in phi direction) = 0 = m (2(r dot)(phi dot) + r (phidoubledot))
F(r) = -N cos a = m( (r double dot - r* (phi dot)^2) [N = normalforce]
F(z) = -mg + N sin a = m (z double dot)

How should I proceed next ? I have to find the equations of motionfor r and phi.
And how should I show that L is a constant of motion?

b) I have no idea how to do this part!

PHY 2048 Lecture Notes - Lecture 4: Net Force, Friction, Centripetal Force

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