Chapter 4 Laws of Motion Problems Solutions

2.  A football punter accelerates a football from rest to a speed of 10 m/s during the time in which his toe is in contact with the ball (about 0.20s).  If the football has a mass of 0.50 kg, what average force does the punter exert on the ball?

From V = Vo + at, the acceleration given to the football is:

3.  A 6.0-kg object undergoes an acceleration of 2.0 m/s^2.  (a) What is the magnitude of the resultant force acting on it? (b) If this same force is applied to a 4.0 kg object, what acceleration is produced?  Full solution is provided.

4.  One or more external forces are exerted on each object enclosed ina dashed box shown in the figure below. Identify the reaction to each of these forces. 

The forces listed in the picture above are as followed:

(a)

Action: The hand exerts a force to the right on the spring. Reaction: The spring exerts an equal magnitude

force to the left on the hand. Action: The wall exerts a force to the left on the spring. Reaction: The spring

exerts an equal magnitude force to the right on the wall. Action: Earth exerts an downward gravitational force

on the spring. Reaction: The spring exerts an equal magnitude gravitational force upward on the Earth.

(b)

Action: The handle exerts a force upward to the right on the wagon. Reaction: The wagon exerts an equal

magnitude force downward to the left on the handle. Action: Earth exerts an upward contact force on the

wagon. Reaction: The wagon exerts an equal magnitude downward contact force on the Earth. Action: Earth

exerts an downward gravitational force on the wagon. Reaction: The wagon exerts an equal magnitude

gravitational force upward on the Earth.

(c)

Action: The player exerts a force upward to the left on the ball. Reaction: The ball exerts an equal magnitude

force downward to the right on the player. Action: Earth exerts an downward gravitational force on the ball.

Reaction: The ball exerts an equal magnitude gravitational force upward on the Earth.

(d)

Action: M exerts a gravitational force to the right on m. Reaction: m exerts an equal magnitude gravitational

force to the left on M.

(e)

Action: The charge +Q exerts an electrostatic force to the right on the charge . Reaction: The charge

exerts an equal magnitude electrostatic force to the left on the charge +Q.

(f)

Action: The magnet exerts a force to the right on the iron. Reaction: The iron exerts an equal magnitude force

to the left on the magnet.

5.  A bag of sugar weighs 5.00 lb on Earth. What would it weigh in Newtons on the Moon, where the free-fall acceleration is one-sixth that on Earth? Repeat for Jupiter, where g is 2.64 times that on Earth. Find the mass of the bag of sugar in kilograms at each of the three locations. The weight of the bag of sugar on Earth is