Un malabarista actua en un recinto cuyo techo est´a 3 m arriba del nivel de sus manos. Lanza una pelota hacia arriba de modo que apenas llega al techo. Calcule:

a) ¿Que velocidad inicial tiene la pelota?
b) ¿Cuanto tiempo tarda la pelota en llegar al techo?
Ahora bien, en el instante en que la primera pelota llega al techo, el malabarista lanza una segunda pelota hacia arriba
con una velocidad inicial de 6 m/s.
c) Cuando han transcurrido 0.4 s desde el lanzamiento de la segunda pelota, ¿a que altura sobre el punto de lanzamiento estan ambas pelotas?
d) ¿A que altura sobre el punto de lanzamiento se cruzan las dos pelotas?

For problems 1-3, consider a simple dc brush motor with a permanent magnet stator. with an an consider a simple dc brush motor with a permanent magnet ae supply voltage of 100 v, the no-load speed of the motor is 1000 rpm. this motor can provide a torque of 1.9 n-m at 800 rpm drawing a current of 2 a current are both zero at no load.) 1. with an armature supply voltage of 100 v, the motor is operated at 900 rpm. what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input? what is the energy efficiency of the motor? with an armature supply voltage of 100 v, the motor is operated at 1100 rpm (where it acts as a generator). what torque input is required? what mechanical power is required what current is generated? what is the electrical power generated? what is the energy efficiency of the motor acting as a generator? 2. with an armature supply voltage raised to 120 v, the motor is operated at 1000 rpm. what is the no-load speed? what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input what is the energy efficiency of the motor? 3.

The free body diagram shows a box being pulled to the left up a 25-degree incline. the magnitude of the normal force is

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?