A sled slides across level snow, slowing. Friction does -40 J of work on it.
A minus sign on an amount of energy: what is it saying about the sled?
Friction acts against the sled's motion, so its work carries the negative sign from the last lesson.
Recall what positive work does: the work done on an object equals the energy transferred to it.
A rope doing +40 J of work on a sled hands the sled 40 J.
So friction doing -40 J on the sled leaves the sled with 40 J less energy of motion.
Friction does -25 J of work on a skateboard rolling along a path. Does friction add energy to the skateboard or remove energy from it?
Read a signed work in two parts. The size says how much energy moves. The sign says which way it moves.
+40 J: the force adds 40 J to the object. -40 J: the force removes 40 J from it.
A braking force does -150 J of work on a go-kart. Enter how many joules of energy the braking force removes from the go-kart.
A rope tow does +300 J of work on a snow tuber. What happens to the tuber's energy?
The work is positive, so the force adds energy to the tuber.
The size of the work says how much: 300 J.
The rope tow adds 300 J of energy to the tuber.
Air resistance does -55 J of work on a paraglider during a descent. What happens to the paraglider's energy?
The work is negative, so the force removes energy from the paraglider.
The size of the work says how much: 55 J.
Air resistance removes 55 J of energy from the paraglider.
Talia says: 'A force that does -75 J of work on a wagon removes 75 J of energy from the wagon.' Is Talia correct?
Friction does -90 J of work on a mountain bike coasting along a trail. Which statement is correct?
Water resistance does -480 J of work on a canoe gliding toward a dock. Enter how many joules of energy the water resistance removes from the canoe.
A library cart slows after Romy lets go, while friction does negative work on it. Why does the cart end up with less energy of motion?