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Lesson 8 Work • Work – when a force acts on an object and it moves some distance. WORK = Force (N) x Distance (m) L8 WORK Alice pulls a sled with a force of 12 N. She pulls the sled through a distance of 5 m. How much work does Alice do on the sled? L8 WORK Work = force x distance Work = 12 N x 5 m = 60 N-m L8 WORK Michael lifts his book bag, which weighs 25 N, from the floor to a desktop that is 0.80 m above the floor. How much work does Michael do on the bag? L8 WORK Force x Distance = WORK 25 N x 0.80 m = 20.0 N-m L8 Inquiry 8.1 Calculating the Work Done on Different Surfaces SURFACE TABLETOP WAXED PAPER PAPER TOWEL FINE SANDPAPER COARSE SANDPAPER L8 EFFORT FORCE (N) EFFORT DISTANCE (m) WORK DONE (N-m) • 1. What force are you working against when you lift a backpack? • L 8.1b • 2. In which of the following cases is work, as defined by scientists, being done? • A. Someone tries to move a piano, but the piano won’t budge. • L 8.1b • B. A tow truck is pulling a car slowly along the street. • L8.1b • C. A student is studying for a mathematics exam. L 8-1b • D. A student is pushing a grocery cart around a store. • L 8.1b • E. Another student is standing in line holding a 12-N bag of potatoes. • L 8.1b • F. A student pushes against the school building. • L 8.1b Lesson 8 Question – Lesson 8 • Is the motor capable of doing enough work to lift the sled to a distance of .10 m? • Lesson 8 • If _________________,then __________ because _________________. • Lesson 8 • • • • Materials 1. 2. 3. • Lesson 8 Lifting a Load • 1. Motor force with three batteries in series: _________________ • 2. Work done by a motor when it lifts a load 10.0 cm. (0.10 m) • Work = _______ x _______ = ______ L 8-2 3. Weight of six washers:______________ 4. Work to raise six washers: Work = ______ x _______ = _______ 5. Your estimate of sled’s weight: _______ 6. Sled’s actual weight: _________ L 8-2 7. Work to lift sled 10.0 cm. (0.10 m): Work = _________ x ______ = _______ L 8-2 • Lesson 8 Vocabulary – Lesson 8 • What happens when an object changes its position by moving in the direction of the force that is being applied is (62) work. • Work = force x distance (w = fd) • Work involves a force applied across a distance. • The metric unit of work is the (63) newton-meter (N-m). • A newton-meter is also a (64) joule (J). • James Joule – described the relationship between work and energy. L8 Vocabulary – Lesson 8 • A force is applied to lift the sled. This is the (65) effort force. • The distance the sled moves is the (66) effort distance. Vocabulary – Lesson 8 • Electric current flows through the wire. The unit used to describe how much electric current flows through a wire is the (67) ampere (amp). • Andre Ampere • The electric potential of a battery is measured in (68) volts. • Alessandra Volta