Hello!
Let's begin by doing a summation of torques, placing the pivot point at the attachment point of the rod to the wall.
We have two torques acting on the rod:
- Force of gravity at the center of mass (d = 0.700 m)
- VERTICAL component of the tension at a distance of 'L' (L = 2.200 m)
Both of these act in opposite directions. Let's use the equation for torque:
Doing the summation using their respective lever arms:
Our unknown is 'theta' - the angle the string forms with the rod. Let's use right triangle trig to solve:
Now, let's solve for 'T'.
Plugging in the values:
C im pretty sure?.........
Power = (force) x (distance / time) = force x speed .
We know the force = 800N.
We have a speed = 30km/hr, but in order to use it in the power formula,
it has to be in meters/second, so we have some work to do first.
(30 km/hr) x (1,000 m/km) x (1 hr / 3,600 sec) = 300 / 36 m/sec .
Power = (force) x (speed) = (800 N) x (300/36 m/s) = <em>6-2/3 kilowatts </em>
Work = (power) x (time) = (6,666-2/3 joule/sec) x (25sec) = <em>166,666-2/3 joules</em>.
The figure for power is slightly weird ... 746 watts = 1 horsepower,
so the truck's engine is only delivering about 8.9 horsepower.
Very fuel-efficient, but I don't think they drive trucks that way.
