Physics question

I know that the vertical component at t=0 is 0 and at t=3.4s it has a positive value. But Is this a straight line or curved ?

I know that the vertical component at t=0 is 0 and at t=3.4s it has a positive value. But Is this a straight line or curved ?

Hint: What does the gradient of a velocity-time graph represent?

As soon as the ball is fired, a *somewhat constant* gravitational force acts on the ball, pulling it downwards.

This means that the velocity increases, but it increases steadily (more importantly, it increases by 9.81 m/s per second).

This should tell you that the line would be a straight line, and the slope would in fact be the acceleration due to gravity (a constant).

thanks for the explanation.

I always have problems with these graph questions. I can't figure out if the line is going to be straight or curved.

Here is a last one. :P

As soon as the ball is fired, a *somewhat constant* gravitational force acts on the ball, pulling it downwards.

This means that the velocity increases, but it increases steadily (more importantly, it increases by 9.81 m/s per second).

This should tell you that the line would be a straight line, and the slope would in fact be the acceleration due to gravity (a constant).

I always found these questions given to students to be odd and confusing. For example, without the air resistance, the object could conceivably just continue to accelerate to increasingly higher velocities until it impacts the ground. This was actually similar to a question asked on stack about whether a terminal velocity existed on the moon, since it had little to no atmosphere to create the drag force:
https://physics.stackexchange.com/questions/320608/terminal-velocity-on-the-moon-is-it-possible-and-how-long-would-it-take

It also suggests that the projectile component would continue to move in the x-direction with the initial horizontal speed. It is even taught like this:
https://www.physicsclassroom.com/class/vectors/Lesson-2/Horizontal-and-Vertical-Components-of-Velocity

Now don't get me wrong, I am aware assumptions had to be made, but I always thought it would be better to teach us students by giving us a value of drag in Newtons, say $D = 10N$, to work with. This way, at least conceptually, the problem relates better to physical intuition.

Probably the most difficult thing I found to get my head around is that the acceleration is constant. So I then considered to then just work on the basis of Newton's First Law - that a body moving at constant velocity has a balance of forces. It then becomes easier to recognize that one of the forces is the acceleration due to gravity and the other is just the drag, which at this stage students would assume is constant for simplicity. The term g, at least close to the surface of the Earth, remains constant, so if the mass is fixed, the gravitational force due to gravity is approximately constant!