University:
Harvard University
Course:
PHYSICS 19 | Introduction to Theoretical Physics
Academic year:

2019
Views:

66

Pages:

7
Author:

blakestar2o1o

Physics Notes - Net Force Practice Problems 1) A 270,000 kg rocket in gravity-free space expels 270 kg of fuel by exerting a force of 360 N on it. Find the magnitude of the acceleration of: a) the fuel b) the rocket For numbers 2-7, draw a free-body diagram of each object that includes ALL the forces that act on the object, and then find the magnitude and direction of the acceleration. 2) A 20.0 kg box is pulled to the left with a force of 10.0 N across a frictionless surface. 20.0 kg 3) A 14.5 kg box is pulled to the right with a force of 40.0 N across a rough surface, which applies a friction force of 11.0 N acting on the box. 14.5 kg 4) A 2.70 kg box is pulled to the left with a force of 12.0 N. It moves at a constant velocity of 2.00 m/s to the left. 2.70 kg 5) A 15 kg box sits still on a rough inclined plane (no math required here). 6) A 60.0 kg student is in free-fall (neglect air resistance). 7) A 60.0 kg student is falling at terminal velocity (when the object has been falling for so long, in the real world, that the force of air resistance matches the weight in magnitude). 8) A 100.0 kg sign is suspended from a pole by two vertical strings which are equidistant from the sign's center. Find the magnitude of the tension in each string. T_{1} T_{2} EAT AT JOE'S 9) A second sign (mass= 25kg ) is suspended from the first by a single string. Find the magnitude of the tension in each of the three strings now. For problems 10-12, draw the free-body diagram for each object. f ind the magnitude of each object's acceleration (magnitude only). Assume all surfaces are frictionless. 10) 25.0 kg F=50.0 N 11) attached by a massless string 20.0 kg 5.00 kg 14) A 6.00 kg box is pulled to the left across a frictionless surface by a force of 20.0 N directed at 45° above the horizontal. The box does not move vertically. 20.0 N 45.0° 6.00 kg a) Resolve the 20.0 N vector into its horizontal and vertical components, using the trigonometric functions. b) Determine the magnitude of the normal force (will it be equal to the weight?). c) Determine the magnitude and direction of the acceleration.