A 5.00-kg block of ice is sliding across a frozen pond. A 7.60-N force is applie

Question

A 5.00-kg block of ice is sliding across a frozen pond. A 7.60-N force is applied in the direction of motion, and the ice block slides 15.0 m (a) Find the work done by the applied force (b) Find the work done by frictional force(f_k = 7 N). A bicycle wheel is being tested at a repair shop. The angular velocity of the wheel is 4.00 rad/s at time t = 0, and its angular acceleration is constant and equal to -1.20 rad/s^2. What is the wheel's angular velocity at time t = 3.00 s? Through what angle does the wheel rotate in 3.00s?

Explanation / Answer

8)a)Work=Force x Distance

Work= 7.60N x 15m
Work= +114J

Since the direction of the force and the direction of the movement are the same, the sign is positive.

b)Work done by the kinetic friction = -fk x d = -7 x 15 =-105 J

9)a)

9) a) ? = ?0 + ?t

Here, ?0 = 4.00 rad/s

Angular acceleration, ? = -1.20 rad/s2

time period, t = 3 s

Hence, ? = 4.00 -1.20(3) = 0.4 rad/s2

b)

? = ?0 + ?0t +1/2 ?t2

= 0 + 4.00 *3 + ½ *0.4*9

        = 12 + 1.8 = 13.8

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