Projectile and Velocity
What force(s) acts on a baseball as it is thrown in the air?
gravity, friction
The tendency for an object to keep the same rate of motion is called __________ ?
inertia
Friction produces (thermal, radiant or mechanical) energy?
thermal
What happens to a car with a negative acceleration?
Car is slowing down
A joule is a unit of _______?
work
If a projectile (tennis ball) is launched at 45 degrees with no gravity, what will happen to the tennis ball?
It will continue moving at 45 degrees.
What is Newton's first law?
Newton’s first law is the law of inertia. It states that an object at rest will remain and rest and an object in motion will remain in motion.
What force works against friction?
inertia
Acceleration can speed things up, slow things down or _____?
Change direction
What is the equation for work?
W = F x d
If you kick a football and there are no forces acting on it, what will happen to the football?
Keep moving
What is the equation for Newton's second law?
Newton’s second law of motion says that when you see an object accelerating there must be external force acting on it. Simply put Newton’s second law is force = mass * acceleration
If it took you 5 seconds to move a rock 15 meters using a force of 150 Newtons, how much power did you need to use
Power = work / time so (150 * 15) / 5 = 450 joules/sec
What is the acceleration if change in velocity is 5m/s and the time is 20 s?
Velocity divided by time which equals 0.25 m/s.
A watt is an unit of _______?
power
What is velocity versus speed?
Speed = distance / time
Velocity = displacement / time
Velocity also considers direction, not just distance over time
What is opposite force to pushing off the ground to jump?
The ground pushing off your foot
What are two ways friction can be reduced?
Change its shape, lubrication, surface smoothness
If a car has a mass of 200 kilograms and produces a force of 500 N, how fast will the car accelerate?
Acceleration =force / mass. 500/200= 2.5 m/s2
What is the equation for power?
P = Work done/ time
If a bike rider travels 15 miles in 30 hours what is his velocity if it is constant?
To determine velocity divide displacement by time: 15/30 = 0.5 miles per hour
What is an example of Newton's third law of motion?
For every action there is an equal and opposite reaction.
Why would someone who lifts less weight than you, be more powerful?
Power depends on the amount of weight and the time it takes to lift the weight so if the person lifts the weight more quickly, they may be more powerful.
How does increasing a car's mass affect how it rolls down a hill?
When the mass of a car is increased it will roll down a ramp quicker. The additional mass is adding to the force that is pulling down on the car. This causes the car to accelerate faster.
A Newton can be written as what unit?
A unit of force, 1 kg × m/s2