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World-class sprinters can accelerate out of the starting blocks with an acceleration that is nearly horizontal and has a magnitude of 15m/s2.

How much horizontal force must a sprinter of mass 48.0kg exert on the starting blocks to produce this acceleration?

Which body exerts the force that propels the sprinter, the blocks or the sprinter?

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

A 77 kg sprinter is running the 100 m dash. At one instant, earlyin the race, his acceleration is 4.7 m/s^2.

1. What total force does the track surface exert on the sprinter?Assume his acceleration is parallel to the ground. Give your answeras a magnitude.

2. What total force does the track surface exert on the sprinter?Assume his acceleration is parallel to the ground, and give youranswer as an angle with respect to the horizontal.

3. This force is applied to one foot (the other foot is in theair), which for a fraction of a second is stationary with respectto the track surface. Because the foot is stationary, the net forceon it must be zero. Thus the force of the lower leg bone on thefoot is equal but opposite to the force of the track on the foot.If the lower leg bone is 60 degrees from horizontal,what is thecomponents of the leg’s force on the foot in the direction parallelto the leg? (Force components perpendicular to the leg can causedislocation of the ankle joint.)

4. What is the components of the leg’s force on the foot in thedirection perpendicular to the leg?

Any help will be appreciated. Thanks :)

Part A.

Blocks A, B, and C are pushed across a frictionless table by a hand that exerts a constant horizontal force. Block A has mass 2M block B has mass 3M and block C has mass M.

a) Draw separate free-body diagrams for each of the three blocks. Clearly label the forces. in the spaces below, draw vectors to represent the net force on each block.
b) Draw the vectors with correct relative magnitudes.

Part B.

Blocks A and B are at rest on a level, frictionless surface. Block B is attached to an ideal massless spring of constant k, which is initially at its equilibrium length. Block B has greater mass than block A (mB > mA).

During the interval from t1 to t2 a hand pushes block A to the left with a constant force of magnitude F0, compressing the spring a distance as shown. At time t2, both blocks again have a speed of zero.

Consider system A consisting of block A and system BS consisting of block B and the spring.

c) During the interval from t1 to t2, is the absolute value of the net work done on system BS by external forces, greater than, less than, or equal to that done on system A by external forces?

 

 

At some later time, the hand is holding the blocks at rest with the spring compressed a distance d0. At time t3 the hand releases the blocks. At time t4, the spring returns to its equilibrium length and both blocks have speed vf, as shown.

Consider the interval from t3 to t4:

d) Is the change in kinetic energy of system BS greater than, less than, or equal to that of system A?
e) Is the change in total energy of system BS positive, negative, or zero?

c) During the interval from t1 to t2, is the absolute value of the net work done on system BS by external forces, greater than, less than, or equal to that done on system A by external forces?

 

 

At some later time, the hand is holding the blocks at rest with the spring compressed a distance d0. At time t3 the hand releases the blocks. At time t4, the spring returns to its equilibrium length and both blocks have speed vf, as shown.

Consider the interval from t3 to t4:

d) Is the change in kinetic energy of system BS greater than, less than, or equal to that of system A?
e) Is the change in total energy of system BS positive, negative, or zero?

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