Question

Velocity-time graph of a block of mass 100g sliding on a horizontal concrete floor under the action of a constant force of 5N is shown below.the magnitude of frictional force acting on the block due to the floor is

Answer 1

4N is the answer....

Answer 2

From the velocity time graph (see attached document),

initial velocity = U = 0 m/s

final velocity = V = 80 m/s

time taken to travel that distance = 8 s

Now we can use 1st linear motion equation to get value for acceleration(a)

[tex]V = U + at[/tex]

$80 = 0 + 8a$

$a = 10 m/s^{2}$

Then we can calculate net force(F) by using Newton's second law,

F = ma

$F = 100*10^{-3} * 10$

$F = 1 N$

But we know that,

Net Force = Constant Force - Frictional Force

$1 = 5 - f$

$f = 5-1$

$Frictional Force = f = 4 N$