Explanation:
We have,
Ajoba and Prav drive to work. Ajoba drives 45 miles in 2.5 hours. Prav drives 74 km in 1 hour 15 min.
1 mile = 1.6 km
45 miles = 72.42 km
74 miles = 119.0 km
1 hour 15 min means 1.25 hours
Average speed of Ajoba is :
Average speed of Prav,
Difference in average speed of Ajoba and Prav is :
So, the difference in average speed of Ajoba and Prav is 66.24 km/h.
a) The work done is 920 J
b) The work done is 5200 J
Explanation:
a)
In this first part of the problem, the crate is moved horizontally at constant speed.
The work required in this case is given by
where
F is the magnitude of the force applied
d is the displacement of the crate
is the angle between the direction of the force and of the displacement
Here the crate is moved at constant speed: this means that the acceleration of the crate is zero, and so according to Newton's second law, the net force on the crate is zero: this means that the force applied, F, must be equal to the force of friction (but in opposite direction), so
F = 230 N
The displacement is
d = 4.0 m
And the angle is , since the force is applied horizontally. Therefore, the work done is
b)
In this case, the crate is moved vertically. The force that must be applied to lift the crate must be equal to the weight of the crate (in order to move it a constant speed), therefore
F = W = 1300 N
The displacement this time is again
d = 4.0 m
And the angle is , since the force is applied vertically, and the crate is moved also vertically. Therefore, the work done on the crate this time is
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