What characteristic is shared by sunspots, solar flares, and coronal mass ejections? Select the two correct responses.(1 point) They appear as dark spots on the sun's surface.

They tend to occur during active periods of the solar cycle.

They are caused by outward fluctuations of the sun's magnetic field.

They appear as bright spots on the sun's surface.

Abearing is designed to a reduce friction b. support a load c.guide moving parts such as wheels, shafts and pivots d. all of the above

Which are examples of projectile motion? choose all that apply a. a soccer ball rolling across the ground in the northeast direction b. a car turning a corner, so it is heading south c. a javelin flying through the air d. a tennis ball lobbed over the net

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.