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Chapter 4: Q1PE (page 161)

A 63.0 kg sprinter starts a race with an acceleration of 4.20 m/s2. What is the net external force on him?

Short Answer

Expert verified

The net external force is 264.6 N.

Step by step solution

01

Given Data

The given data is listed as below,

  • Mass of the sprinter is, m= 63 kg.

  • Acceleration is, a= 4.20 m/s2.

02

Concept of Newton’s second law of motion

Significant Newton’s second law of motion states that the acceleration of a system is directly proportional to the net external force acting on the system and is inversely proportional to the mass of the system. Mathematically,

Fnet=ma ………. (i)

Here,

(a).Fnetis the net force

(b). mis the mass

(c).a is the acceleration.

03

Determine the net external force acting on the sprinter

Substitute 63 kg for mand 4.20 m/s2 for a in equation (i),

Fnet=63kg×4.20m/s2=264.6kg‐m/s2=264.6N

Hence, the net external force on him is 264.6 N.

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Most popular questions from this chapter

Near the end of a marathon race, the first two runners are separated by a distance of 45 m. The front runner has a velocity of 3.50 m/s, and the second a velocity of 4.20 m/s. (a) what is the velocity of the second runner relative to the first? (b) If the front runner is 250 m from the finish line, who will win the race, assuming they run at constant velocity? (c) What distance ahead will the winner be when she crosses the finish line?

A basketball player jumps straight up for a ball. To do this, he lowers his body 0.300 m and then accelerates through this distance by forcefully straightening his legs. This player leaves the floor with a vertical velocity sufficient to carry him 0.900 m above the floor.

(a) Calculate his velocity when he leaves the floor.

(b) Calculate his acceleration while he is straightening his legs. He goes from zero to the velocity found in part (a) in a distance of 0.300 m.

(c) Calculate the force he exerts on the floor to do this, given that his mass is 110 kg.

Two teams of nine members each engage in a tug of war. Each of the first team’s members has an average mass of 68 kg and exerts an average force of 1350 N horizontally. Each of the second team’s members has an average mass of 73 kg and exerts an average force of 1365 N horizontally.

(a) What is magnitude of the acceleration of the two teams?

(b) What is the tension in the section of rope between the teams?

Unreasonable Results

A 75.0-kg man stands on a bathroom scale in an elevator that accelerates from rest to 30.0 m/s in 2.00 s.

(a) Calculate the scale reading in newtons and compare it with his weight. (The scale exerts an upward force on him equal to its reading.)

(b) What is unreasonable about the result?

(c) Which premise is unreasonable, or which premises are inconsistent?

Describe a situation in which one system exerts a force on another and, as a consequence, experiences a force that is equal in magnitude and opposite in direction. Which of Newton’s laws of motion apply?
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