Download Name_______________ Per_____ IB/AP Physics I – Forces Group

Name_____________________ Per_____ IB/AP Physics I – Forces Group Problems
A. A 90 kg boy is standing on a frozen pond (assume no friction) while
four of his friends pull on him with ropes as shown at left. The diagram
shows the directions of the four forces. Find the resulting motion of the
boy if F1=50N, F2=100N, F3=150N, and F4=60N.
(a) Make an estimate of the net force by adding the four vectors in the
drawing.
(b) Find the net force precisely by using the method of components, then
find the acceleration of the boy.
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B. A boat is pulled along a long, straight canal by two forces, as shown at
left. If the boat is to maintain a constant velocity of 1.0m/sec:
(a) Find the unknown force.
(b) Determine the “drag” force caused by the water.
(c) If this drag force was somehow cut in half, what would happen to the
boat?
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C. A mass M, resting on a table top, is accelerated to the right by a rope
attached to a hanging mass m. The pulley is frictionless and massless. If
the surface of the table top is frictionless:
(a) Write and simplify Newton’s 2nd Law for M.
(b) Write and simplify Newton’s 2nd Law for m.
(c) Combine the two and solve for the acceleration.
(d) Find the expression for T, the tension in the rope.
(e) Find the acceleration of M if µ=0.20, M=2 kg, and m=5 kg.
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D. A 1000kg flatbed truck is carrying a 200 kg refrigerator. The coefficient
of kinetic friction for the truck’s tires is 0.90, and the coefficient of static
friction for the refrigerator on the flatbed is 0.45.
(a) What distance is required for the truck to skid to a stop from a velocity
of 60 miles per hour.
(b) What is the shortest distance required for the truck to accelerate from
zero to 60 miles per hour without the refrigerator sliding?
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E. For the system of two masses shown, M=5kg, m=2kg, and the inclined
plane is frictionless.
(a) Write and simplify Newton’s 2nd Law for M.
(b) Write and simplify Newton’s 2nd Law for m.
(c) Combine and solve for the acceleration.
(d) Find the tension for the connecting rope.
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F. Repeat E if µk – 0.40 for the sliding mass.
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G. A 75.0 kg person stands on a scale in an elevator. What does the scale read (in kg) when: (a) the elevator
is at rest; (b) the elevator is climbing at a constant speed of 3.0m/s; (c) the elevator is falling at 3.0m/s; (d)
the elevator is accelerating up at 3.0m/s2; (e) the elevator is accelerating down at 3.0m/s2?