Answer:
(1) 0.333 Hz
(2) 4 sec
(3) 2 sec, 0.5 Hz
Explanation:
(1) We have given time period of pendulum is 3 sec
So T = 3 sec
Frequency will be equal to 
(2) Frequency of the pendulum is given f = 0.25 Hz
Time period is equal to 
(3) It is given that a pendulum makes 10 back and forth swings in 20 seconds
So time taken to complete 1 back and forth swings = 
So time period T = 2 sec
Frequency will be equal to 
Answer:

Explanation:
Generally from kinematics equations we have that
Here u is the initial velocity of the rock and the value is 0 m/s given that there was no information that it was in motion before the fall
substituting 1.43 s for t and
for g we have that
=> 
The negative sign show that the displacement is in the direction of the negative y-axis
Answer:
D. a heat engine that uses heat to do work
Answer:
A drop of water falling from a faucet into a sink
Complete question is;
Which action would increase the strength of the electric force between the balloon and the water?
A. Holding a magnet near the stream of water
B. Holding the balloon closer to the stream of water
C. Holding a magnet near the balloon
D. Moving the balloon farther away from the stream of water
Answer:
B. Holding the balloon closer to the stream of water
Explanation:
When we take a charged balloon near water, what happens is that it makes electrons to be pushed away which in turn leaves the area to be positively charged. This area is now attracted to the balloon and thus the strength of the electric force between the balloon and the water is increased.