Week 1 Review
Does your mass or weight change when you travel to mars
weight not mass
What is the acceleration of a basketball when it is falling
10 m/s^2
What is one example of a contact force?
Friction, tension, pushing
A force F = 100 N is used to move a crate a distance of 5 m. How much work is done by F?
W = F d = 100 N x 5 m =
= 500 J.
Friction always acts _________(for or against ) motion?
Against
What is the difference between speed and Velocity?
Velocity is speed with a direction
What are the units for acceleration
In Newton’s second law, F = ma, what are the proper units for m, a, and F?
F= Force
m=mass
a=acceleration
Does the kinetic energy of an object depend on which direction it is moving?
No. Ke=1/2 mv^2 so direction doesn't matter
What is the difference between static and Kinetic Friction
Static Friction: A minimum amount of force is needed to get an object to move.
Kinetic Friction: While it is moving, the friction force is called kinetic friction.
What is the difference between mass and weight?
Weight is the force of gravity acting on mass
To hit the center of a target, where should a rifle be aimed?
After a projectile leaves the barrel of a rifle it begins falling under gravity. To hit the center
of the target, you must aim the rifle at a point above center.
A net force of 12 N is applied to a mass of 8 kg. What is the resulting acceleration of the
mass?
1.5 m/s^2
What is the difference between an elastic, and completely inelastic collision?
Inelastic collision is when objects stick together after colliding. loss of KE
Elastic they bounce off and no loss of KE
An object moves in a circular path with constant speed. Is its velocity constant?
No, Velocity is changing direction
Velocity is an example of a (scalar or vector)?
Vector
An object falls from rest what will its velocity be after 5 seconds?
50 m/s.
A car travels at uniform speed in a circle. Is it accelerating?
Yes because it is changing directions
Object A has a mass of 2 kg and moves with a velocity of 15 m/s. It collides with object which has a mass of 4 kg and sticks to it. What is the speed of the combination after the collision?
5 m/s
A mass of 3 kg is attached to a string of length 3 m. If the string can provide a maximum
tension force of 6 N, what is the maximum speed that the mass can be swung in a circle
before the string breaks?
v must be less than 6.
Fc=mv^2/R
_______ is the property all things have to resist change in motion
Inertia
An object is thrown vertically up from the ground with a velocity of 30 m/s. When will it
reach its highest point?
3 s
How does an airbag minimize injury in a collision? (Explain in physics)
Without an airbag, you hit the windshield and stop abruptly causing a large force to be exerted on you causing injury. With the airbag, you stop over a longer time interval which reduces the force and minimizes the injury
A tennis ball on top of a basketball are dropped. When the basketball hits the ground, the tennis ball strongly rebounds upward. Why?
The tennis ball gets a big “kick” because its mass is much less than the mass of the
basketball.
Describe the conversion of kinetic energy into potential energy and vice‐versa as a ball is
thrown upward and then falls back to the ground.
Kinetic energy is the smallest at the top. Potential energy is the highest at the top. And vice versa