On the first day of the 2016 baseball season, David Ortiz of the Boston red Sox

Question

On the first day of the 2016 baseball season, David Ortiz of the Boston red Sox is barring. The pitcher throws the ball, which has a mass of 0.15 kg. toward home plate. When it reaches Ortiz, the ball is travelling horizontally with a velocity of 40 m/s. Ortiz hits the ball with his bat, and the ball files back toward the pitcher with a velocity of 50 m/s at an angle of 30 degree above horizontal. How much work is done by the bat on the ball? A heavy plow is being pulled across a level field by a par of oxen. The plow has mass of 300 kg, and the force from the once is exerted horizontally, parallel to the ground. Between the plow and the ground, the coefficient of static friction is mu_s = 0.4, and coefficient of kinetic friction is mu_s = 0.3. The plow is initially at rest, and the oxen begin to pull with a force of 100 N. Is that force sufficient to get the plow to start moving? Explain your answer. Once they get the plow moving, with what force must the oxen pull to keep the plow moving with a constant velocity of 1.5 m/s? Calvin has constructed a track for his toy train, as shown in the figure below. The train has mass of 0.1 kg. The upper part of the track is h = 0.3 m above the floor. Assume the track is frictionless. The train is initially at rest on the upper part of the track. Calvin pushes it 0.2 m horizontally. In order to get the train moving with a velocity of 2 m/s, how much force much must he apply? The train, now with velocity 2 m/s, then rolls down the slope to the lower section of track. Once it reaches the floor, what is the train's new velocity?

Explanation / Answer

for 2 opening day

work is equal to change in Kinetic energy of that object

and K..E = P2/2m

where P is change in momentum = m(vi- vf) =0.15(40+50cos30)= 12.4951

so work done = 12.49512/2*0.15 = 520.4326 J

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