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Chapter 9: Q. 10 (page 227)

A sprinter accelerates from rest. Is the work done on the sprinter positive, negative, or zero? Explain

Short Answer

Expert verified

Work done on sprinter is negative.

Step by step solution

01

Given information

A sprinter accelerates from rest.

02

Explanation

When sprinter accelerates, the work done on sprinters is due to normal reaction on sprinter.

As the sprinter takes off from ground, work done is calculated by the frictional force acting on when sprinter takes off foot from ground.

So ,the normal reaction on the sprinter is negative giving negative work done on the sprinter.

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Most popular questions from this chapter

Hooke’s law describes an ideal spring. Many real springs are better described by the restoring force (Fsp)s=-k∆s-q(∆s)3, where q is a constant.

Consider a spring with k=250N/m .

It is alsoq=800N/m3.

a. How much work must you do to compress this spring 15cm? Note that, by Newton’s third law, the work you do on the spring is the negative of the work done by the spring.

b. By what percent has the cubic term increased the work over what would be needed to compress an ideal spring? Hint: Let the spring lie along the s-axis with the equilibrium position of the end of the spring at s=0.

Then ∆s = s.

A 0.2 kg plastic cart and a 20 kg lead cart both roll without friction on a horizontal surface. Equal forces are used to push both carts forward a distance of 1 m, starting from rest. After traveling 1 m, is the kinetic energy of the plastic cart greater than, less than, or equal to the kinetic energy of the lead cart? Explain.

Justin, with a mass of 30 kg, is going down an 8.0-m-high water slide. He starts at rest, and his speed at the bottom is 11 m/s. How much thermal energy is created by friction during his descent?

The left end of a spring is attached to a wall. When Bob pulls on the right end with a 200 N force, he stretches the spring by 20 cm. The same spring is then used for a tug-of-war between Bob and Carlos. Each pulls on his end of the spring with a 200 N force.
How far does the spring stretch? Explain.

The two ropes seen in FIGURE are used to lower a 255kg piano 5.00m from a second-story window to the ground. How much work is done by each of the three forces?
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