lunes, 11 de abril de 2011

KINEMATICS EXERCISES

1.- A mouse runs towards its hiding place with a constant speed of 3 m/s. It happens in front of a cat that is quiet and it persecutes it to the cat with an acceleration of 2m/s2. The hiding place is, then, to 12 m of the mouse and which the cat is three meters more back, Will be able the cat to escape?

2.- A driver who marches to 108 km/h sees an obstacle 100 ms and restrains thorough to try to avoid it. If its reaction time is of 0.4 s and the graph of its braking she is the one of the figure:

a) What space will cross before driving the brake?
b) You calculate the space that it has crossed in the time of braking.
c) will hit the driver against the object?




3.- In a cycling stage one of the runners one escapes of the squad and, when he takes an advantage of 5 km, another runner leaves the squad in his persecution. If the speed that takes the saved runner is of 45 km/h and the one of the 50 runner persecutes who it is of km/h:
a) Write the equations of the movement of each, taking like reference the squad.
b) Calculate the position in he will reach which it.
c) Represent his graphs v versus t in the same coordinate system.
4.- You classify the following scalar or vectorial magnitudes like: mass, speed, acceleration, temperature, force, density, pressure
5.- A car stopped in a traffic light starts up when this one is put green. Taking the traffic light like reference, you indicate if the graph s-t would be straight or curved and why.

6.- A cycling march to 25 km/h and restrains before arriving at a curve until a 12 speed of km/h in 2,5 s. What acceleration has suffered? What space has crossed during the braking? If the radius of the wheels is of 35 cm, whereupon speed turns before taking the curve?

7.- The wheel of a bicycle has a perimeter of 3.77 ms and they turn to 50 rpm. Which will be the speed that takes the bicycle, expressed in km/h? How many returns will give in 1 minute?

8.- From a window of 5.5 ms of height a tennis ball with a speed of 4 is sent upwards m/s. You determine it peak altitude at which the tennis ball arrives, the speed with which arrive at the ground, the space that she crosses and the time that is in the air.

9.- From a bridge of 58 ms of height a rubber ball is sent downwards of 70 g of mass with a speed of 3.6 m/s. You determine the speed with which it arrives at the ground and the time that is in the air.

10.- Knowing that the equation of the movement of a moving body is: x=3 + 3t2, in International System Units:
a) Which is the acceleration and the starting point? b) What type of movement takes the moving body?
                           
SOLUTIONS:
1.- No, the cat reaches to 2.4 m from the hiding
2.- a) 12m; b) 56,25m, c) No, he stops to 31.75 m of obstacle
3.- a) e1=5+45t; e2=50t; b) 50km
4.- scalar magnitudes: mass, temperature, density and pressure.
Vectorial magnitudes: speed, acceleration and force
5.- Curve because it is uniformly accelerated rectilinear motion and its equation of position is:
e= v0t+1/2at2
6.- a= -1,4m/s2;  e=12m; w=9,5rad/s
7.- v=11,31km/h; 50returns
8.- ymax=6,316m; t=1,54s; v= -11,13m/s
9.- v= -33,98m/s; t=3,1s
10.- a) a= 6m/s2; b) uniformly accelerated rectilinear motion

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