At the surface of a certain planet, the gravitational acceleration $g$ has a magnitude of $12.0$ m/s$^2$. A $2.10$-kg brass ball is transported to this planet. What is (a) the mass of the brass ball on the Earth and on the planet, and (b) the weight of the brass ball on the Earth and on the planet?

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 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.

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, 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?

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.

A hiker starts at his campsite and walks at 2 m/s northward for 30 min, then turns and walks due west at 1 m/s for 1 h. (a) Calculate the distance the hiker walks in 1.5 h. (b) Calculate the hiker's displacement from the campsite after walking for 1.5 h. (c) Explain the difference between distance and displacement.

A person in a hurry averages $62 \mathrm{MPH}$ on a trip covering a distance of 300 miles. What time was required to travel that distance?

A woman walks a distance of $240 \mathrm{~m}$ with an average speed of $1.2 \mathrm{~m} / \mathrm{s}$. What time was required to walk this distance?

A driver travels at an average speed of $68 \mathrm{MPH}$ for  $2.5$ hours. How far does she travel throughout this period?

When a lawn is mowed two weeks (14 days) after the prior mowing, it is discovered that grass cuttings have an average length of $5.2 \mathrm{~cm}$. What is the typical growth rate of this grass, measured in mathrm cm per day?

A walker completes a  $2.4 \mathrm{~km}$ route in 30 minutes. What is the walker's average speed in  $\mathrm{km} / \mathrm{h}$ for this distance?