# Physics

posted by .

A 0.47 kg pendulum bob is attached to a string 1.2 m long. What is the change in the gravitational potential energy of the system as the bob swings from point A to point B where θ = 31°?

I've tried using PE = mgh but I don't know where the 31 degrees comes in there. I'm confused as to what formula to use.

• Physics -

for simplicity i am going to do this symbolically.

m = .47Kg
l = 1.2m
g = 9.81m/s²
è = 31 degrees

the change in potential energy is

mgÄh

in this problem,
Äh = l-lCos(è)
= l(1-cosè)

(it is 1-cosè becaus cos 90=1.. and its cos 90-cosè)

so

ÄE = mgÄh
= .47Kg * 9.81m/s² * 1.2m * (1-cos31)
and the answer is in units of joules

• Physics -

mgh*

cos theta*

sorry

• Physics -

also Deta E*

• Physics -

Delta* wow i cannot type

• Physics -

@kelly..may i know why have to l-l cos delta?

## Similar Questions

1. ### physics

A 0.34 kg pendulum bob is attached to a string 1.2 m long. What is the change in the gravitational potential energy of the system as the bob swings from point A to point B, where θ = 37°?
2. ### physics

A 0.34 kg pendulum bob is attached to a string 1.2 m long. What is the change in the gravitational potential energy of the system as the bob swings from the bottom of the string, where θ = 37°?
3. ### physics

A 0.33- kg pendulum bob is attached to a string 1.2 m long and hangs vertically as shown in Figure 1. What is the change in the pendulum bob’s gravitational potential energy as it swings from the lowest point of the pendulum to a …
4. ### Physics Classical Mechanics Help ASAP

A pendulum of mass m= 0.8 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
5. ### Classical mechanics

A pendulum of mass m= 0.9 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
6. ### physics help

A pendulum of mass m= 0.8 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
7. ### physics help

A pendulum of mass m= 0.8 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
8. ### PHYSICS(HELP)

A pendulum of mass m= 0.8 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
9. ### physics (Urgent)!!!!!!!!!!!!!!!!!!!!!!

A pendulum of mass m= 0.9 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …
10. ### physics Classical Mechanics

A pendulum of mass m= 0.9 kg and length l=1 m is hanging from the ceiling. The massless string of the pendulum is attached at point P. The bob of the pendulum is a uniform shell (very thin hollow sphere) of radius r=0.4 m, and the …

More Similar Questions