Answer:
0.71 m/s
Explanation:
We find the time it takes the stone to hit the water.
Using y = ut - 1/2gt² where y = height of bridge, u = initial speed of stone = 0 m/s, g = acceleration due to gravity = -9.8 m/s² (negative since it is directed downwards)and t = time it takes the stone to hit the water surface.
So, substituting the values of the variables into the equation, we have
y = ut - 1/2gt²
82.2 m = (0m/s)t - 1/2( -9.8 m/s²)t²
82.2 m = 0 + (4.9 m/s²)t²
82.2 m = (4.9 m/s²)t²
t² = 82.2 m/4.9 m/s²
t² = 16.78 s²
t = √16.78 s²
t = 4.1 s
This is also the time it takes the raft to move from 5.04 m before the bridge to 2.13 m before the bridge. So, the distance moved by the raft in time t = 4.1 s is 5.04 m - 2.13 m = 2.91 m.
Since speed = distance/time, the raft's speed v = 2.91 m/4.1 s = 0.71 m/s
Answer:
we agree with
Edgar: The net force on the ball at the top position is 9 N. Both the tension and the weight are acting downward so you have to add them.
Explanation:
Weight of the ball is given as

so we have


now tension force at the top is given as


Now at the top position by force equation we can say that ball will have two downwards forces
1) Tension force
2) Weight of the ball
so net force on the ball is given as


So we agree with
Edgar: The net force on the ball at the top position is 9 N. Both the tension and the weight are acting downward so you have to add them.
Answer: B. Allegheny plateau
Explanation: Allegheny plateau is a mountainous region that makes up the northern part of the United States of America, the following states are located on the Allegheny plateau New York, Pennsylvania, West Virginia and Ohio, it is made up of HORIZONTAL SEDIMENTARY BEDROCK at elevated lands. Allegheny plateau is over 40million area is over 40million acres,it has been a site for Erosion and for millions years,through this erosions some areas have been brought low while others are higher following the deposition of materials by the erosion.
Answer:
Power = 70 W
Explanation:
Given that,
Force, F = 70 N
Height, h = 5 m
Time, t = 5 s
We need to find the power of the object. We know that,
Power = work done/time
Put all the values,

So, the required power is 70 W.
Answer:
mgh= 10 x 8 x 10
= 800
but you can try 10 x 8 x 4^-1 x 10