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1 answer:
a. 25 joules of work is done by the object.
Explanation:
According to the work-energy theorem, the work done ON an object is equal to the change in kinetic energy of the object, therefore:
where
is the final kinetic energy of the car, with
m = 2 kg being the mass of the car
v = 0 is the final speed of the car (brought to rest)
is the initial kinetic energy of the car, with
u = 5 m/s being the initial speed of the car
Substituting numbers, we find:
The negative sign means that the work done ON the car is negative: this means therefore that the work has been actually done BY the car. In fact, the car has lost its kinetic energy: this means that it has done work on the surrounding, converting its kinetic energy into other forms of energy.
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Answer:
B
Explanation:
Torque exerted on an object depends upon three things.
1. Moment arm
2. Magnitude of applied force
3. Direction of force
T=r x F
T= r * F sinФ
Let T1 is force due to force applied at mid point of door.
let d is the width of door, so
T1= °) (∴ moment arm =d)
T1= __________(2) (∴ sin 90°=1)
Let T2 is the torque due to force applied at the doorknob.
T2= (∴ moment arm =d)
T2= __________(2) (∴ sin 90°=1)
From equation (1) and equation (2)
2T1=T2
or
T1= T2/2
As T2 is greater so option B is the correct answer.