Physics HW 3
If you push for an hour against a stationary wall, you do no work
on the wall
A bow is drawn so that it has 40 J of potential energy. When the arrow is fired its kinetic energy is ideally
40 J.
A moving object has
Energy, velocity, speed, and momentum
When a simple machine multiplies force, it decreases
distance moved
A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is
doubled.
A simple machine CANNOT multiply
energy.
T/F: A hydraulic press properly arranged, like a simple lever, is capable of multiplying energy input.
false
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force to stop the car, the force needed to stop the truck is
greater.
A cannonball fired from a long-barrel cannon will have a greater muzzle velocity because the cannonball receives a greater
impulse.
An object may have potential energy because of its
location
When you are in the way of a fast-moving object and can't get escape, you will suffer a smaller force if the collision time is
long.
Compared with falling on a wooden floor, a wine glass may not break when it falls on a carpeted floor because of
longer time to stop.
When a cannon fires a cannonball at a given speed, the smaller recoil speed of the cannon is due to different
masses
A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater
momentum
It is correct to say that impulse is equal to
the change in momentum
In order to catch a fast-moving softball with your bare hand, you extend your hand forward just before the catch an then let the ball ride backward with your hand. Doing this reduces the catching force because the
time of catch is increased.
The distinction between impulse and force involves the
time the force acts
If you push an object twice as far while applying the same force, you do
twice as much work
When you push an object a certain distance while applying twice the force, you do
twice as much work
If you do work on an object in half the time, your power output is
twice.
