Download 04 freebody word problems

04 word problems for Newton's second law
October 03, 2013
Newton's Law Word Problems
Tips
• for each problem, draw the freebody diagram
• determine if you have to use the motion information to find the object's acceleration or if you have to use information on the forces to find the net, unbalanced force.
• don't forget about units and directional arguments
Ex. John is accelerating from rest to a speed of 60 km/h in 4.0 seconds. If you can assume no friction, determine the force created by the car?
ƩFi = Fnet = ma
1. What net force is required to accelerate a car at a rate of 2 m/s2 if the car has a mass of 3,000 kg a) if there was no friction? (6 000 N)
b) if frictional forces were 2 000 N, what is the applied force? (8 000 N)
2. A 10 kg bowling ball would require what force to accelerate down an alleyway at a rate of 3 m/s2? (30 N)
3. What is the mass of a falling rock if it produces a force of gravity of 147 N? (what is the rate of acceleration of an object in freefall) (15 kg)
4. What is the mass of a truck if it produces a force of 14,000 N against a frictional force of 4 000 N while accelerating at a rate of 5 m/s2 ? (2 000 kg)
5. What is the acceleration of softball (while it is stopping) if it has a mass of 0.5 kg and hits the catcher's glove with a force of 25 N? (ignore the force of gravity) (50 m/s2)
6. How would the question be different if you included the force of gravity in your analysis in question 5? (You do not have to solve this problem.) 7. Sally's car has a mass of 2000 kg. If her car produces a force of 5000 N, to accelerate the car at 1.2 m/s2, what is the force of friction? (2 600 N)
8. Sally wants to accelerate even faster than in problem #7, so she removes 500 kg of mass from her car. How fast will her 1500 kg car accelerate if it produces 5000 N of force against the same force of friction?
(1.6 m/s2) 9. A 12 kg ball is pulled toward the centre of earth by the force of gravity (Fg = mg) as it falls through a pool of water. a) If the buoyant force (the force exerted by the water on the ball) is 40 N, at what rate does the ball accelerate? (6.5 m/s2) b) If the ball was dropped and the pool is 2 m deep, how long does it take to reach the bottom and how fast is it going when it hits the bottom? (0.78 s, 5.1 m/s) 1
04 word problems for Newton's second law
October 03, 2013
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04 word problems for Newton's second law
October 03, 2013
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