A diving platform drops a steel ball (with an initial velocity of zero). Using  $g=10 \mathrm{~m} / \mathrm{s}^2$ and an approximation of its value: a. What is the ball's velocity 0.07 seconds after it is reset? b. After it is released, what velocity  $1.4$ is it travelling at?

A mass of 3.0 kg is acted upon by three forces of 4.0 N, 6.0 N and 9.0 N and is in equilibrium. Convince yourself that these forces can indeed be in equilibrium. The 9.0 N force is suddenly removed. Determine the acceleration of the mass.

A single force of $40 \mathrm{~N}$ acts upon a $5-\mathrm{kg}$ block. What is the magnitude of the acceleration of the block?

A net force of $100\hspace{0.5mm}\mathrm{N}$ acts upon a crate and produces an acceleration of $4.0\hspace{0.5mm}\mathrm{m/s^{2}}$. What is the weight of the crate on the earth?

The law of inertia states that no force is required to maintain motion. Why, then do you have to keep pedaling your bicycle to maintain motion?

Which of the following best describes an application of Newton's first law? a. When one object strikes another object, there is an equal and opposite force. b. As the force on an object increases, the acceleration of the object increases. c. An object rolling along a flat surface with no friction will keep moving at the same velocity

Newton's first law states that no force is required to maintain motion in a straight line at constant speed. If Newton's first law is true, why must you continue to pedal a bicycle on a level surface to keep moving?

Newton’s second law states that the total force on an object equals the object’s mass times its acceleration. Express Newton’s second law in terms of the momentum of an object instead of its acceleration.

A car driver applies the brakes, causing the vehicle's velocity to decrease. Does the car accelerate during this process, according to the definition of acceleration provided in this chapter? Explain.

Starting from rest, a car accelerates at a rate of $4.2 \mathrm{~m} / \mathrm{s}^2$ for a time of 5 seconds. What is its velocity at the end of this time?

The velocity of a car decreases from $30 \mathrm{~m} / \mathrm{s}$ to $18 \mathrm{~m} / \mathrm{s}$ in a time of 4 seconds. What is the average acceleration of the car in this process?

Starting from rest and moving in a straight line, a runner achieves a velocity of $7 \mathrm{~m} / \mathrm{s}$ in a time of $2 \mathrm{~s}$. What is the average acceleration of the runner?

A car traveling with constant speed travels 150 km in 7200 s. What is the speed of the car?

A hiker walks 3.00 km north and then 4.00 km west, all in one hour and forty minutes. Calculate his average speed in km/h.