Answer:
A
Explanation:
The answer would be A because when feet push down on anything, the force will push down the skateboard
21) Acceleration from D to E: 
22) The acceleration of the bus from D to E is 
Explanation:
21)
The acceleration of an object is equal to the rate of change of velocity of the object. Mathematically:

where
u is the initial velocity
v is the final velocity
t is the time elapsed
In this problem, we want to measure the acceleration of the bus from point D to point E. We have:
- Initial velocity at point D: u = 0
- Final velocity at point E: v = 5 m/s
- Time elapsed from D to E: t = 21 - 16 = 5 s
Therefore, the acceleration between D and E is

22) This question is the same as 21), so the result is the same.
Learn more about acceleration:
brainly.com/question/9527152
brainly.com/question/11181826
brainly.com/question/2506873
brainly.com/question/2562700
#LearnwithBrainly
Answer:
The coefficient is 0.90
Explanation:
Drawing a diagram makes thing easier, we will assume that the acceleration tends to zero because it start barely moving.

Answer:
a. P.E = 3430Joules.
b. Workdone = 3430Nm
Explanation:
<u>Given the following data;</u>
Mass = 70kg
Distance = 5m
We know that acceleration due to gravity is equal to 9.8m/s²
To find the potential energy;
Potential energy = mgh
P.E = 70*9.8*5
<em>P.E = 3430J</em>
b. To find the workdone;
Workdone = force * distance
But force = mass * acceleration
Force = 70*9.8
Force = 686 Newton.
Workdone = 686 * 5
<em>Workdone = 3430Nm</em>
Answer:
Explanation:
This is a problem based on time dilation , a theory given by Albert Einstein .
The formula of time dilation is as follows .
t₁ = 
t is time measured on the earth and t₁ is time measured by man on ship .
A ) Given t = 20 years , t₁ = ? v = .4c

=1.09 x 20
t₁= 21.82 years
B ) Given t = 5 years , t₁ = ? v = .2c

=1.02 x 5
t₁= 5.1 years
C ) Given t = 10 years , t₁ = ? v = .8c

=1.67 x 10
t₁= 16.7 years
D ) Given t = 10 years , t₁ = ? v = .4c

=1.09 x 10
t₁= 10.9 years
E ) Given t = 20 years , t₁ = ? v = .8c

=1.67 x 20
t₁= 33.4 years