Answer:
a) 1450watts
b) 564watts
c) 1.11
Explanation:
Power consumed = IV
I is the current rating
V is the operating voltage
If a blow-dryer and a vacuum cleaner each operate with a voltage of 120 V and the current rating of the blow-dryer is 12 A, while that of the vacuum cleaner is 4.7 A then their individual power rating is calculated thus;
a) For blow-dryer
Operating voltage = 120V
Its current rating = 12A
Power consumed = IV
= 120×12
= 1440watts
b) For vacuum cleaner:
Operating voltage is the same as that of blow dryer = 120V
Its current rating = 4.7A
Power consumed = IV
= 120×4.7
= 564watts
c) Energy used = Power consumed × time taken
Energy used = Power × time
Energy used by blow dryer = 1440×20×60
= 1,728,000Joules
Energy used up by vacuum cleaner = 564×46×60
= 564×2760
= 1,556,640Joules
Ratio of the energy used by the blow-dryer in 20 minutes to the energy used by the vacuum cleaner in 46 minutes will be 1,728,000/1,556,640 = 1.11
A single fixed pulley can be used to raise or lower lightweight objects.
Option b
<u>Explanation:</u>
A pulley is a simple machine tool which is used to make lifting or lowering tasks easy. A single fixed pulley is a system involving only one pulley fixed on a constant rigid support with a rope wrapped around the wheel. Such a system can be used only to change the direction of applied force in raising or lowering small, lightweight objects which need minimal work force.
A single fixed pulley system helps only in redirecting the applied force direction by using a rope and wheel assembly. The work done in such a case remains the same and hence it is not preferred to use it in lifting heavy objects. Neither is the required force reduced in case of a single fixed pulley system. A movable pulley helps in achieving (A) and (C).
D because gamma rays and ultra violet rays are one of the examples of the three ways to transfer heart which is convection, radiation, and conduction.
Answer:
Explanation:
Let l be th length of pendulum
loss of height
= mg ( l - l cos50)
= mg l ( 1-cos50)
1/2 mv² = mgl ( 1-cos50)
v = √[2gl( 1- cos50)]
= √( 2 x 9.8 x .7 x ( 1-cos50)
= 2.2 m / s
speed at the bottom = 2.2 m /s
b )
centripetal acceleration
= v² / r
= 2.2 x 2.2 / .7
= 6.9 m /s²
C )
If T be the tension
T - mg = mv² / r
T = mg + mv² / r
= .13 X 9.8 + .13 X 6.9
= 2.17 N
