(C)
Explanation:
The circle has a radius r = 0.5 m, which means that its circumference C is

One revolution means that the stopper travels a distance equal to the circumference of the circle so the velocity of the stopper is

Answer:
The ball will be at 700 m above the ground.
Explanation:
We can use the following kinematic equation
.
where y(t) represent the height from the ground. For our problem, the initial height will be:
.
The initial velocity:
,
take into consideration the minus sign, that appears cause the ball its thrown down. The same minus appears for the acceleration:

So, the equation for our problem its:
.
Taking t=6 s:
.
.
.
.
.
So this its the height of the ball 6 seconds after being thrown.
Answer:
The mass of the object is 24.5 kg and weight of the object on Mars is 91.14 N.
Explanation:
Weight of the object on the surface of Earth, W = 245 N
On the surface of Earth, acceleration due to gravity, g = 10 m/s²
Weight of an object is given by :
W = mg
m is mass

So, the mass of the object is 24.5 kg
Acceleration due to gravity on Mars, g' = 3.72 m/s²
Weight of the object on Mars,
W' =mg'
W' = 24.5 kg × 3.72 m/s²
= 91.14 N
So, the weight of the object on Mars is 91.14 N.
Answer:
Time taken = 10400 s
Explanation:
Given:
Initial speed of the train, 
Final speed of the train, 
Displacement of the train, 
Using Newton's equation of motion,

Now, using Newton's equation of motion for displacement,

Now, plug in the value of
in the above equation. This gives,

Now, plug in 234000 m for
, 25 m/s for
and 20 m/s for
. Solve for
.

Therefore, the time taken by the train is 10400 s.
PE = 0.5 × k × x²
PE potential Energy
k spring constant
x stretch/compression of the spring