newton laws
Kids were playing with balls which are of equal mass. They kicked them with different forces. Which one accelerated more?
Red ball – 10N Blue ball – 3N Yellow ball - 5N
Red ball since force and acceleration are directly related
As friction increases, what happens to momentum?
It decreases
Any object thrown into space upon which the only acting force is gravity is known as
Projectile
Which of the following best defines distance?
The total amount of ground covered by an object
The horizontal acceleration of a projectile is ALWAYS?
Zero!
A man is whirling a 0.5 kg ball on a 1.0 m long string at 2 m/s. What is true about the force on the ball?
It pushes forward, tangent to the circle
When will the momentum of an isolated system remain conserved?
external force on the system is zero
A ball is kicked with an initial velocity of 12m/s at angle of 50° to the horizontal.
How long will the ball stay in the air (assume it strikes the ground at the same height it was launched)
1.88sec
If an object has a constant velocity, what can be said about its acceleration?
The acceleration is zero
What is an object's change in momentum equal to?
the impulse acting on the object
A student is drawing a free body diagram for the following scenario: "A penguin accelerates by sliding down an icy hill on its belly."
What else should her drawing include and why?
It should include an arrow pointing upward, perpendicular to the ramp, because the normal force represents the support force of the surface.
What is the kinetic energy of a 60 kg man running at 8 m/s?
1920j
K=1/2 x 60kg x(8m/s)^2
Path taken by a projectile is known as
Projectile motion
Which of the following represents the relationship between velocity and time for an object moving with constant acceleration?
A linear graph a parabolic graph a linear graph
A linear graph
A stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following BEST describes why no injury occurs?
The bag provides the necessary force to stop the person
There is a force F acting on an object of mass m, which has an acceleration a. If the mass is doubled and the force is reduced by a factor of four, what is the acceleration of the new object?
a= 1/8
A student hits a hockey puck with a hockey stick and the puck speeds up. Another student claims that the student broke the Law of Conservation of Momentum because the puck gained momentum.
Which of these is the BEST explanation of why the Law is not broken in this closed system?
The hockey stick loses as much momentum as the puck gained.
In a Projectile Motion, the simultaneous independent rectilinear motions are
Along x and y axis
Can an object's average velocity equal zero when object's speed is greater than zero?
Yes, when the object moves in a straight line at a constant rate
Which is more work, pushing with 115N over 15m or lifting 20kg 10m?
W=F x D
115n x 15m= 1725j 20n x 10m=200j
Pushing with 115N over 15m is more work.
What happens according to Newton if you let an untied balloon go?
3rd Law
Air will rush out of the balloon forcing the balloon to move through the air in
the opposite direction, but equal in force.
A large, moving truck crashes into a small parked car. How do the magnitudes of the impulses and the forces on each vehicle compare during the collision?
The truck experiences equal force and equal impulse
A cannon is fired horizontally from the top of a 30m cliff into the ocean. The initial velocity of the cannon was 1000m/s. How far from the cliff does the cannon ball hit the water?
2470m
How tall is a building if a ball dropped from rest takes 9 seconds to hit the ground?
405m tall
if you put 500j into a machine but only get 400j out, how efficient is the machine?
(400j/500j) x 100 =80%