Answer:
Approximately
.
Explanation:
<h3>Solve this question with a speed-time plot</h3>
The skateboarder started with an initial speed of
and came to a stop when her speed became
. How much time would that take if her acceleration is
?
.
Refer to the speed-time graph in the diagram attached. This diagram shows the velocity-time plot of this skateboarder between the time she reached the incline and the time when she came to a stop. This plot, along with the vertical speed axis and the horizontal time axis, form a triangle. The area of this triangle should be equal to the distance that the skateboarder travelled while she was moving up this incline until she came to a stop. For this particular question, that area is approximately equal to:
.
In other words, the skateboarder travelled
up the slope until she came to a stop.
<h3>Solve this question with an SUVAT equation</h3>
A more general equation for this kind of motion is:
,
where:
and
are the initial and final velocity of the object,
is the constant acceleration that changed the velocity of this object from
to
, and
is the distance that this object travelled while its velocity changed from
to
.
For the skateboarder in this question:
.
Answer:
The coefficient of static friction between the box and floor is, μ = 0.061
Explanation:
Given data,
The mass of the box, m = 50 kg
The force exerted by the person, F = 50 N
The time period of motion, t = 10 s
The frictional force acting on the box, f = 30 N
The normal force on the box, η = mg
= 50 x 9.8
= 490 N
The coefficient of friction,
μ = f/ η
= 30 / 490
= 0.061
Hence, the coefficient of static friction between the box and floor is, μ = 0.061
Answer:
B. 4 m/s
Explanation:
v=d/t
Running for 300 m at 3 m/s takes 100 seconds and running at 300 m at 6 m/s takes 50 seconds. 100 s + 50 s = 150 s (total time). Total distance is 600 m, so 600 m/ 150 s = 4 m/s.
The lines of magnetic field from a bar magnet form closed lines. By convention, the field direction is taken to be outward from the North pole and in to the South pole of the magnet.