Weight equals mass times gravitational acceleration=400N, so mass=400/9.8=41kg approx.
Answer:
Yes we can find the initial velocity of car without finding acceleration.
u = 10 m/s.
Explanation:
Given that
s=20 m
Car takes 4 s to come in rest.
We know that when acceleration is constant then we can apply motion equation
----------1
------2
From equation 1 and 2

So we can say that

Given that the velocity of car at final condition will be zero (v=0)


From the above equation we can find the initial velocity of car without finding the acceleration

u = 10 m/s
Answer:
The net force on the scooter is 95 N to the left.
Explanation:
Lizzie is pushing with 75 N of force to the left, so the force is a vector with 75N of magnitude and to the left.
Alex is helping with 20 N to the left, so the force is a vector with 20 N magnitude and to the left.
When we add vectors, vectors that point in the same direction add up and vectors that point in opposite directions are subtracted.
Hence, the net force is equal to:
F=75 N + 20 N=95 N
As both forces point to the left, the net force is also to the left.
To solve the problem it is necessary to apply the concepts related to the conservation of energy through the heat transferred and the work done, as well as through the calculation of entropy due to heat and temperatra.
By definition we know that the change in entropy is given by

Where,
Q = Heat transfer
T = Temperature
On the other hand we know that by conserving energy the work done in a system is equal to the change in heat transferred, that is

According to the data given we have to,




PART A) The total change in entropy, would be given by the changes that exist in the source and sink, that is



On the other hand,



The total change of entropy would be,



Since
the heat engine is not reversible.
PART B)
Work done by heat engine is given by



Therefore the work in the system is 100000Btu
Answer:
0.0367
Explanation:
The loss in kinetic energy results into work done by friction.
Since kinetic energy is given by
KE=0.5mv^{2}
Work done by friction is given as
W= umgd
Where m is the mass of suitacase, v is velocity of the suitcase, g is acceleration due to gravity, d is perpendicular distance where force is applied and u is coefficient of kinetic friction.
Making u the subject of the formula then we deduce that

Substituting v with 1.2 m/s, d with 2m and taking g as 9.81 m/s2 then

Therefore, the coefficient of kinetic friction is approximately 0.0367