Initial velocity (u) = 0 m/s
Final velocity (v) = 25 m/s
time taken (t) = 10s
acceleration (a) = ?
Now,
Acceleration is rate of change of velocity, so formula is
a = (v - u)/t
a = (25 - 10)/10
a = 15/10
a = 1.5 m/(s^2)
Use this value of a.
according to newton's third law, every action has equal and opposite reaction. in this scenario of making a jump from the boat onto a dock, as i jump my feet in contact with the boat push the boat in backward direction. hence the action force is the push by my feet on the boat. the boat reacts by applying a reaction force on my feet pushing the feet in forward direction. hence reaction force here is the force by the boat on the feet. due to the reaction force of the boat on feet, i am pushed in forward direction to reach the the dock.
Answer:
B. 560 J
J. 1.2 m
Explanation:
v = Final velocity = 0
u = Initial velocity = 4 m/s
= Coefficient of friction = 0.7
m = Mass of runner = 70 kg
g = Acceleration due to gravity = 
Kinetic energy is given by

The mechanical energy lost is 560 J
Acceleration is given by

From kinematic equations we get

The runner slides for 1.2 m

b) Finding total distance :
Distance travelled from 0 s to 5 s :
Distance travelled from 5 s to 10 s :
Distance travelled from 10 s to 15 s :
- 150 + 1/2 x 5 x 5
- 150 + 12.5 = 162.5 m
Distance travelled from 15 s to 20 s :
- 36 x 5 + 1/2 x 5 x 4
- 180 + 10 = 190 m
Distance travelled from 20 s to 25 s :
- 45 x 5 + 1/2 x 5 x 5
- 225 + 12.5 = 237.5 m
Distance travelled from 25 s to 30 s :
- 40 x 5 + 1/2 x 10 x 5
- 200 + 25 = 225 m
Distance travelled from 30 s to 35 s :
- 20 x 5 + 1/2 x 20 x 5
- 100 + 50 = 150 m
Distance travelled from 35 s to 40 s :
Total = 75 + 150 + 162.5 + 190 + 237.5 + 225 + 150 + 50
Total = 1240 m
c) velocity at t = 15 s
d) average velocity
- 0 m/s (as displacement is equal to 0)
e) average speed
f) Part d uses displacement whereas part e uses distance
Explanation:
Displacement is the shortest distance between two points. Displacement is used to calculate vector quantities such a velocity, force, acceleration, etc.
Here, Maria drove to the store and then to work this means that her total displacement will be the minimum distance between her initial point and her work place.
Hence, the minimum distance between her initial point and her work place is her total displacement.