Romy drags a pallet across a warehouse floor. Friction of 15 N acts on the pallet, against its motion, while the pallet slides 2 m.
How much work does friction do on the pallet, sign included?
First the size. The size of the work is force times distance: 15 × 2 = 30, so 30 J.
Then the sign. Friction points against the pallet's motion, so its work is negative.
The work done by friction on the pallet is -30 J.
With the force in newtons and the distance in meters, the work comes out in joules.
Two steps, every time: multiply for the size, then attach the sign from the direction.
A rope's force of 40 N acts on a raft, with the motion, while the raft moves 3 m. Calculate the work done by the rope's force on the raft.
Write down the values:
force = 40 N, distance = 3 m, work = ?
Write down the equation:
work done = force × distance
Substitute in the values, and calculate:
work done = 40 × 3 = 120
The force acts with the motion, so the work done is +120 J.
Air resistance of 8 N acts on a cyclist, against the motion, over 25 m. Calculate the work done by air resistance on the cyclist.
Write down the values:
force = 8 N, distance = 25 m, work = ?
Write down the equation:
work done = force × distance
Substitute in the values, and calculate:
work size = 8 × 25 = 200
The force acts against the motion, so the work done is -200 J.
A rope's force of 50 N acts on a canoe, with the motion, while the canoe moves 6 m. Enter the work done by the rope's force on the canoe in J.
Friction of 20 N acts on a sliding crate, against its motion, over 5 m. Enter the work done by friction on the crate in J. Use a minus sign for negative work.
Air resistance of 9 N acts on a racing cyclist, against the motion, over 40 m. Enter the work done by air resistance on the cyclist in J. Use a minus sign for negative work.
A pinecone of weight 2 N falls 7 m from a branch. Its weight acts downward, with the motion. Enter the work done by the weight on the pinecone in J.
A winch cable's force of 60 N raises a water bucket 9 m up a well shaft, with the motion. Enter the work done by the cable's force on the bucket in J.
A braking force of 75 N acts on a scooter, against its motion, over 2 m. Enter the work done by the braking force on the scooter in J. Use a minus sign for negative work.
A drag mat is towed around a baseball infield. The towing force of 35 N acts on the mat, with its motion, through 12 m. Enter the work done by the towing force on the mat in J.
A parcel slides 3 m down a mailroom chute while friction of 45 N acts on it, against its motion. Enter the work done by friction on the parcel in J. Use a minus sign for negative work.
Ugo lowers a paint can on a rope from a scaffold. The can's weight of 25 N acts downward while the can moves 7 m downward. Enter the work done by the weight on the can in J.