# Physics

posted by .

A boy sits in a tire that is attached to a rope that passes over a pulley fastened to the ceiling and then passes back down to the boy's hands. The weight of the boy plus the tire is W. The force with which the boy must pull on the free end of the rope to support his weight in the tire is:

(a) (1/2)W
(b) W
(c) 2W
(d) (2/3)W
(e) (3/2)W

• Physics -

Well, downward forces are W, and upward forces are his Pull, and tension.

So his pull + Tension=W on the tire side.
On the other side, tension=Pulling force
so
Pull+tension=W
Pull+ Pull=W
do the math.

• Physics -

Ok, I think I got it. Are these free body diagrams correct? (ignore the dots)

TIRE+BOY:

T F
|.|
.|
W

FREE END:

.T
.|
.|
.F

SYSTEM:

.F
.|
.|
.T.....(This tension is down)
T.F....(This tension is up)
|.|
.|
.W

CANCELING TENSIONS:

2F
|
|
W

2F=W so F=(1/2)W

• Physics -

Now I'm confused. Why does changing the direction of a force double it? I'm also confused about whether the tension is a reaction to the weight of the tire and the boy or the force that the boy pulls down on the rope with. Also if the force in the free body diagram of the system were another person pulling the tire and the boy up, why would the force not be half the weight in that case?

## Similar Questions

1. ### Physics

Note: I am in Algebra-based Physics Two 35.0 N weights are suspended at opposite ends of a rope that passes over a light, frictionless pulley. The pulley is attached to a chain that is fastened to the ceiling. Start solving this problem …
2. ### Physics for Life science

A boy climbs up an 8.00m high tree. To come back down, the boy slides down along a rope. The coefficient of friction between the rope and the boy is 0.40. What is the velocity with which the boy reaches ground?

A 43.3 kg boy and a 60.0 kg girl are on the surface of a frozen lake, 10.5 m apart. Using a rope, the boy exerts a horizontal 5.90 N force on the girl, pulling her toward him. Calculate the magnitude of the boy's acceleration.
4. ### Physics

A 43.3 kg boy and a 60.0 kg girl are on the surface of a frozen lake, 10.5 m apart. Using a rope, the boy exerts a horizontal 5.90 N force on the girl, pulling her toward him. Calculate the magnitude of the boy's acceleration.
5. ### physics

A pulley is attached to the ceiling (as shown in the figure below). Spring scale A is attached to the wall and a rope runs horizontally from it and over the pulley. The same rope is then attached to spring scale B. On the other side …
6. ### physics

1) Two people sit on a park bench 6.0 ft long, weighing 160 lb. A boy weighing 75lb sits directly over the legs on the left side. A man weighing 170 lb sits 2.0 ft to the right of the boy. How much weight is supported by each leg on …
7. ### physics

1. A 100 lb body is pulled up an inclined plane making an angle of 37 degrees with the horizontal by the rope that passes over the pulley at the top of the plane and is fastened to a 70lb. weight. Neglecting the effect of friction, …
8. ### physics

A 50 foot see-saw has 4 kids sitting on it. A 62 lb. girl sits on the left end, with a 76 lb. girl sitting 2.5 feet in front of her. On the right side, a 96 lb. boy sits on the end and has another boy sitting 2.5 feet in front of him. …
9. ### Math

I can't figure this out! Help please! The Problem At the local park, I saw a man was quizzing a boy with some simple arithmetic problems, and the boy seemed to be getting them all correct. He asked the boy, "32 + 5", and the boy answered, …
10. ### physics

a sea saw consist of a uniform bar 4m long and of mass 2kg. a boy of weight 42N sits at end of the sea saw while another boy of weight 38N sits at the end of the season. at what point must the season be pivoted if it is to balance. …

More Similar Questions