Forces and Motions

A girl lets go of her backpack, and it falls toward the ground. Which is the best explanation for why the backpack moves toward the ground?

• friction pull on the backpack
• gravity pulls on the backpack
• the girl exerts a force on the backpack
• the backpack's mass increase

• period 1
• period 2
• period 3
• period 4

Which is the best way to use the x-axis on a distance-time graph?

• to represent the position of an object that travels
• to represent the period of time that an object travels
• to represent the speed at which an object travels
• to represent the distance that an object travels

A student rolls a ball down a smooth wooden ramp and observes what happens. Then he puts sandpaper on the ramp and rolls the ball again. What is the student most likely investigating?

• the effect of change in gravity on the ball's motion
• the effect of a change in mass on the ball's motion
• the effect of a change in friction on the ball's motion
• the effect of a change in a ball's motion on the ramp

A student forms a ball out of clay. Then he pushes the ball and observes its motion along his desk. If he repeats the activity, what should he do to make the ball move faster?

• change the ball's starting position
• change the ball's shape
• make the ball heavier
• push the ball harder

Jose and Sarah both leave school for the library at 3pm. Jose rides his bike at a speed of 16 kilometers per hour. Sarah rides her bike at a speed of 14 kilometers per hour. Which will most likely happen?

• they will ride in two different directions
• Jose will arrive at the library before Sarah
• Sarah will arrive at the library before Jose
• They will arrive at the same time

A bat flies three kilometers. A scientist wants to find the bat's speed. Which other information does the scientist need?

• the bat's starting position 
• the bat's mass while flying
• the direction the bat flies
• the amount of time the bat flies

Four shoppers are pushing identical shopping carts through a store at the same speed. Each cart contains a different object. Which cart will require the least force to stop its motion?

• the cart containing an object with a mass of 700 g
• the cart containing an object with a mass of 530 g
• the cart containing an object with a mass of 390 g
• the cart containing an object with a mass of 180 g