Work Power Energy Test

Result

Work Power Energy Test - 2

Score
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Rank
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Weekly Quiz Competition

Question 1
1 / -0

What happens when a machine is lubricated with oil?

A
the mechanical efficiency of machine increases

B
the mechanical advantage of the machine increases

C
both its mechanical advantage and efficiency increases

D
its efficiency increases, but its mechanical advantage decreases

Solution

Value of µ_k ( kinetic friction decreases ) therefore less energy is wasted as heat; hence efficiency increases.
Question 2
1 / -0

A body of mass 2 kg is being dragged on a rough horizontal plane with a uniform velocity of 2 m/s. The coefficient of friction between the body and the surface is 0.20, J = 4.2 J/cal and g = 9.8 m/s². Calculate the amount of heat generated in 5 s.

A
9.33 cal

B
3.45 cal

C
7.35 cal

D
5.80 cal

Solution

s = v t = 2 × 5 = 10m

Q = work done against friction

= μmgs = 0.2 × 2 × 9.8 × 10

= 39.2 J = 9.33 cal