Log in
Physics
1
answer
0
watching
58
views
23 Nov 2019

A pendulum is 0.767m long and the bob has a mass of 1.47 kg. At thebottom of its swing, the bob's speed is 1.75 m/s. What is thetension in the string at the bottom of ths string?

Why is the tension greater than the weight of the bob? Select fromthe following statements, which one's are true and which one's arefalse.

1. True or False-The bob has an upward acceleration, so the net Fymust be upward and greater than the weight of the bob.
2. True or False Since the bob is moving and its velocity ischanging the tension must be greater than the weight.
3. True or False The bob has a downward acceleration, so the Fymust be downward and greater than the weight of the bob.
4. True or False If the bob were at rest, the tension would beequal to the weight of the bob.

Watch
1
answer
0
watching
58
views

For unlimited access to Homework Help, a Homework+ subscription is required.

Nestor Rutherford
Nestor RutherfordLv2
13 Jul 2019

Unlock all answers

Get 1 free homework help answer.
Already have an account? Log in
Share

Related textbook solutions

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

Related questions

A ball of mass m is attached to a string of length L. It is swungin a vertical circle with enough speed to keep the string tautthroughout the motion. Assume the ball travels freely in the circlewith negligible loss of mechanical energy. Determine if thefollowing six statements are true or false.


1. The acceleration of the ball at the top of the circle isdirected `up'.
2. The tension in the string at the top of the circle can begreater, equal, or less than the weight of the ball, depending onthe speed of the ball.
3. The magnitude of the difference between the kinetic energy ofthe ball at the top and the bottom of the circle is 2mgL.
4. mvb2/L = Tb+mg, where vb and Tb are the speed of the ball andthe tension of the string at the bottom of the circle.
5. The tension in the string is less at the top of the circle thanat the bottom of the circle.
6. The difference between the tensions at the top and at the bottomof the circle is independent of the speed of the ball.

This problem introduces the concept of tension. The example is a rope, oriented vertically, that is being pulled from both ends. Let Fu and Fd (with u for up and d for down) represent the magnitude of the forces acting on the top and bottom of the rope, respectively. Assume that the rope is massless so that its weight is negligible compared with the tension. (This is not a ridiculous approximation-modern rope material such as Kevlar can carry tensions thousands of times greater than the weight of tens of meters of such rope.)

Consider the three sections of rope labeled a, b, and c in the figure.

  • At point 1, a downward force of magnitude Fad acts on section a.
  • At point 1, an upward force of magnitude Fbu acts on section b.
  • At point 1, the tension in the rope is T1.
  • At point 2, a downward force of magnitude Fbd acts on section b.
  • At point 2, an upward force of magnitude Fcu acts on section c.
  • At point 2, the tension in the rope is T2.

(A) What is the magnitude Fad of the downward force on section a?

(B) What is the magnitude Fbu of the upward force on section b?

(C) The magnitude of the upward force on c, Fcu, and the magnitude of the downward force on b, Fbd, are equal because of which of Newton's laws?

(D) The magnitude of the force Fbu is ______ Fbd.

(E) Now consider the forces on the ends of the rope. What is the relationship between the magnitudes of these two forces?

(a) Fu > Fd

(b) Fu = Fd

(c) Fu < Fd

(F) The ends of a massless rope are attached to two stationary objects (e.g., two trees or two cars) so that the rope makes a straight line. For this situation, which of the following statements are true?

(a) The tension in the rope is everywhere the same.

(b) The magnitudes of the forces exerted on the two objects by the rope are the same.

(c) The forces exerted on the two objects by the rope must be in opposite directions.

(d) The forces exerted on the two objects by the rope must be in the direction of the rope.


1.

While helping a friend move, you push a 11.5 kg dolly with a forceof 11.0 N. Assume there are no other forces acting on the dolly. Ifthe dolly starts at rest, how far does it move in 3.50 s?
1 m

2.

At a lumberjack competition an axe with a mass of 1.25 kg is thrownat a target with a speed of 41 m/s. When it hits the target, itpenetrates to a depth of 0.055 m.
(a) What was the average force exerted by the target on theaxe?
1 N

(b) If the mass of the axe is halved, and the force exerted by thetarget on the axe remains the same, by what multiplicative factordoes the penetration depth change?
2
It doubles. It increases by a factor of the square root of two. Itdoes not change. It decreases by a factor of the square root oftwo. It halves.
Your work in question(s) will also be submitted or saved.
3

Your 1500 kg car pulls a 540 kg trailer away from a stop sign withan acceleration of 2.00 m/s2. (Note the answers should be given inkN.)
(a) What is the net force exerted by the car on the trailer?
1 kN

(b) What force does the trailer exert on the car?
2 kN

(c) What is the net force acting on the car?
3 kN


4.

Two boxes sit next to, and touching, each other on a frictionlesshorizontal surface. The lighter box has a mass of 5.31 kg and theheavier box has a mass of 7.29 kg.
(a) Find the contact force between these boxes when a horizontalforce of 6.1 N is applied to the light one.
1 N

(b) If the 6.1 N force is applied to the heavy box instead, is thecontact force between the boxes the same as, greater than, or lessthan the contact force in part (a)?
2

(c) Verify your answer to part (b) by calculating the contact forcein this case.
3 N

5.

A child sits in a wagon and together they have a mass of 25 kg. Thewagon is pulled with a constant speed by a handle that is at anangle of 22° above the horizontal. If the normal force exerted onthe wagon is 210 N, what is the force F applied to thehandle?
1 N

6.

An object acted on by three forces moves with constant velocity.One force acting on the object is in the positive x direction andhas a magnitude of 6.7 N; a second force has a magnitude of 4.5 Nand points in the negative y direction. Find the direction andmagnitude of the third force acting on the object.
1 N
2° (counterclockwise from the +x axis)


7.

A chain is used to lift a 1200 kg car vertically upward with anacceleration of 0.90 m/s2. What is the tension in the chain?
1 N

8.

A 22.5 kg box (m1) rests on a table.

(a) What is the weight of the box?
1 N
What is the normal force acting on it?
2 N (upward)
(b) A 12.5 kg box (m2) is placed directly on top of the 22.5 kgbox.
Determine the normal force that the table exerts on the 22.5 kgbox.
3 N (upward)
Determine the normal force that the 22.5 kg box exerts on the 12.5kg box.
4 N (upward)

9.

Your friend has a weight of 127 lb when standing on a scale. Youtake the scale to an elevator where you notice your friend's weighton the scale reads 108 lb. What are the direction and magnitude ofthe elevator's acceleration?
Direction 1
Magnitude 2 m/s2

10.

When you lift a package with a force of 82 N, the packageaccelerates upward at a rate of a. If, instead, you lift with aforce of 93 N, the package now has an acceleration of 8 multipliedby a.
(a) Find the weight of the package.
1 N

(b) Find the acceleration a.
2 m/s2

11.

One 3.1 kg paint bucket is hanging by a massless cord from another3.1 kg paint bucket, also hanging by a massless cord, as shownbelow.

(a) If the buckets are at rest, what is the tension in eachcord?
(lower cord) 1 N
(upper cord) 2 N

(b) If the two buckets are pulled upward with an acceleration of1.30 m/s2 by the upper cord, calculate the tension in eachcord.
(lower cord) 3 N
(upper cord)5

12)
Your friend has a pair of fuzzy dice with a mass of 1.32 g hangingfrom his rear-view mirror.
(a) When he accelerates from a stoplight, the dice deflect backwardtoward the rear of the car hanging at an angle of 6.18° relative tothe vertical. Find the tension in the string holding thedice.
N

(b) At what angle to the vertical will the tension in the string betwice the weight of the dice?
°


Weekly leaderboard

Home
Homework Help 3,900,000
Physics 110,000
Start filling in the gaps now
Log in