Newtonovi zakoni gibanja - Univerza v Novi Gorici
Newtonovi zakoni gibanja - Univerza v Novi Gorici
Newtonovi zakoni gibanja - Univerza v Novi Gorici
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<strong>Newtonovi</strong> <strong>zakoni</strong> <strong>gibanja</strong><br />
<strong>Univerza</strong> v <strong>Novi</strong> <strong>Gorici</strong><br />
Fakulteta za aplikativno naravoslovje<br />
Inˇzenirska fizika (I. stopnja)<br />
Fizika I<br />
2008/2009<br />
VAJE<br />
11.11.2008<br />
1. A worker drags a crate across a factory floor by pulling on a rope tied to the crate. The worker<br />
exerts a force of 450N on the rope, which is inclined 38 ◦ to the horizontal, and the floor exerts<br />
a horizontal force of 125N that opposes the motion. Calculate the acceleration of the crate (a)<br />
if its mass is 310kg and (b) if its weight is 310N.<br />
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2. An object is hung from a spring balance attached to the ceiling of an elevator. The balance<br />
reads 65N when the elevator is standing still. What is the reading when the elevator is moving<br />
upward (a) with a constant speed 7.6m/s and (b) with a speed 7.6m/s while decelarating at a<br />
rate of 2.4m/s 2 ?<br />
3. A 1kg mass on 37 ◦ is connected to a 3kg mass on a horizontal surface. The surfaces and the<br />
pulley are frictionless. If F = 12N, what is the tension in the connecting cord?<br />
4. A block of mass m1 = 3.7kg on a frictionless inclined plane of angle 30 ◦ is connected by a cord<br />
over a massless, frictionless pulley to a second block of mass m2 = 2.3kg hanging vertically.<br />
What are (a) the magnitude of the acceleration of each block and (b) the direction of the<br />
acceleration of m2? (c) What is the tension in the cord?<br />
1<br />
F<br />
F
5. A 100kg crate is pushed at constant speed up a frictionless 30 ◦ ramp. (a) What horizontal force<br />
F is required? (b) What force is exerted by the ramp on the crate?<br />
6. A 52kg circus performer is to slide down a rope that will snap if the tension exceeds 425N<br />
(a) What happens if the performer hangs stationary on the rope? (b) At what magnitude of<br />
acceleration does the performer just avoid breaking the rope?<br />
7. A 5kg block is pulled along a horizontal frictionless floor by a cord that exerts a force F = 12N<br />
at an angle α = 25 ◦ above the horizontal. (a) What is the acceleration of the block? (b) The<br />
force F is slowly increased. What is its value before the block is lifted (completely) off the floor?<br />
(c) What is the acceleration of the block just before it is lifted (completely) off the floor?<br />
2<br />
F
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